zlib is a Ruby interface for the zlib compression/decompression library. Versions 3.0.0 and below, 3.1.0, 3.1.1, 3.2.0 and 3.2.1 contain a buffer overflow vulnerability in the Zlib::GzipReader. The zstream_buffer_ungets function prepends caller-provided bytes ahead of previously produced output but fails to guarantee the backing Ruby string has enough capacity before the memmove shifts the existing data. This can lead to memory corruption when the buffer length exceeds capacity. This issue has been fixed in versions 3.0.1, 3.1.2 and 3.2.3.

The remote MiracleLinux 9 host has packages installed that are affected by multiple vulnerabilities as referenced in the AXSA:2026-1667:01 advisory.

    * zlib: zlib: Memory corruption via buffer overflow in Zlib::GzipReader (CVE-2026-27820)
      * net-imap: Net::IMAP: Arbitrary IMAP command injection via CRLF sequences in unvalidated input     (CVE-2026-42257)
      * ruby/net-imap: ruby: Net::IMAP: Denial of Service via large iteration count in SCRAM authentication     (CVE-2026-42256)
      * net-imap: Net::IMAP: Command injection via non-synchronizing literals (CVE-2026-47240)
      * net-imap: Net::IMAP: Arbitrary IMAP command injection due to improper input validation     (CVE-2026-47242)
      * net-imap: rubygem-net-imap: Net::IMAP: Denial of Service via malformed command input (CVE-2026-47241)

Tenable has extracted the preceding description block directly from the MiracleLinux security advisory.

Note that Nessus has not tested for these issues but has instead relied only on the application's self-reported version number.

The remote RockyLinux 8 host has packages installed that are affected by multiple vulnerabilities as referenced in the RLSA-2026:50728 advisory.

    * zlib: zlib: Memory corruption via buffer overflow in Zlib::GzipReader (CVE-2026-27820)

    * net-imap: Net::IMAP: Arbitrary IMAP command injection via CRLF sequences in unvalidated input     (CVE-2026-42257)

    * ruby/net-imap: ruby: Net::IMAP: Denial of Service via large iteration count in SCRAM authentication     (CVE-2026-42256)

    * net-imap: Net::IMAP: Command injection via non-synchronizing literals (CVE-2026-47240)

    * net-imap: Net::IMAP: Arbitrary IMAP command injection due to improper input validation (CVE-2026-47242)

    * net-imap: rubygem-net-imap: Net::IMAP: Denial of Service via malformed command input (CVE-2026-47241)

    Bug Fix(es) and Enhancement(s):

    * ruby:3.3/ruby: Rebase to the latest Ruby 3.3 release [rhel-8] (JIRA:Rocky Linux-170929)

Tenable has extracted the preceding description block directly from the RockyLinux security advisory.

Note that Nessus has not tested for these issues but has instead relied only on the application's self-reported version number.

The remote RockyLinux 10 host has packages installed that are affected by multiple vulnerabilities as referenced in the RLSA-2026:50778 advisory.

    * zlib: zlib: Memory corruption via buffer overflow in Zlib::GzipReader (CVE-2026-27820)

    * net-imap: Net::IMAP: Arbitrary IMAP command injection via CRLF sequences in unvalidated input     (CVE-2026-42257)

    * ruby/net-imap: ruby: Net::IMAP: Denial of Service via large iteration count in SCRAM authentication     (CVE-2026-42256)

    * net-imap: Net::IMAP: Command injection via non-synchronizing literals (CVE-2026-47240)

    * net-imap: Net::IMAP: Arbitrary IMAP command injection due to improper input validation (CVE-2026-47242)

    * net-imap: rubygem-net-imap: Net::IMAP: Denial of Service via malformed command input (CVE-2026-47241)

    Bug Fix(es) and Enhancement(s):

    * ruby: Rebase to the latest Ruby 3.3 release [rhel-10.2.z] (JIRA:Rocky Linux-211300)

Tenable has extracted the preceding description block directly from the RockyLinux security advisory.

Note that Nessus has not tested for these issues but has instead relied only on the application's self-reported version number.

The remote RockyLinux 10 host has packages installed that are affected by multiple vulnerabilities as referenced in the RLSA-2026:50773 advisory.

    * zlib: zlib: Memory corruption via buffer overflow in Zlib::GzipReader (CVE-2026-27820)

    * net-imap: Net::IMAP: Arbitrary IMAP command injection via CRLF sequences in unvalidated input     (CVE-2026-42257)

    * ruby/net-imap: ruby: Net::IMAP: Denial of Service via large iteration count in SCRAM authentication     (CVE-2026-42256)

    * net-imap: Net::IMAP: Command injection via non-synchronizing literals (CVE-2026-47240)

    * net-imap: Net::IMAP: Arbitrary IMAP command injection due to improper input validation (CVE-2026-47242)

    * net-imap: rubygem-net-imap: Net::IMAP: Denial of Service via malformed command input (CVE-2026-47241)

    Bug Fix(es) and Enhancement(s):

    * ruby4.0: Rebase to the latest Ruby 4.0 release [rhel-10.2.z] (JIRA:Rocky Linux-211310)

Tenable has extracted the preceding description block directly from the RockyLinux security advisory.

Note that Nessus has not tested for these issues but has instead relied only on the application's self-reported version number.

The remote RockyLinux 9 host has packages installed that are affected by multiple vulnerabilities as referenced in the RLSA-2026:50828 advisory.

    * zlib: zlib: Memory corruption via buffer overflow in Zlib::GzipReader (CVE-2026-27820)

    * net-imap: Net::IMAP: Arbitrary IMAP command injection via CRLF sequences in unvalidated input     (CVE-2026-42257)

    * ruby/net-imap: ruby: Net::IMAP: Denial of Service via large iteration count in SCRAM authentication     (CVE-2026-42256)

    * net-imap: Net::IMAP: Command injection via non-synchronizing literals (CVE-2026-47240)

    * net-imap: Net::IMAP: Arbitrary IMAP command injection due to improper input validation (CVE-2026-47242)

    * net-imap: rubygem-net-imap: Net::IMAP: Denial of Service via malformed command input (CVE-2026-47241)

    Bug Fix(es) and Enhancement(s):

    * ruby:3.3/ruby: Rebase to the latest Ruby 3.3 release [rhel-9.8.z] (JIRA:Rocky Linux-171335)

Tenable has extracted the preceding description block directly from the RockyLinux security advisory.

Note that Nessus has not tested for these issues but has instead relied only on the application's self-reported version number.

The remote RockyLinux 9 host has packages installed that are affected by multiple vulnerabilities as referenced in the RLSA-2026:50827 advisory.

    * zlib: zlib: Memory corruption via buffer overflow in Zlib::GzipReader (CVE-2026-27820)

    * net-imap: Net::IMAP: Arbitrary IMAP command injection via CRLF sequences in unvalidated input     (CVE-2026-42257)

    * ruby/net-imap: ruby: Net::IMAP: Denial of Service via large iteration count in SCRAM authentication     (CVE-2026-42256)

    * net-imap: Net::IMAP: Command injection via non-synchronizing literals (CVE-2026-47240)

    * net-imap: Net::IMAP: Arbitrary IMAP command injection due to improper input validation (CVE-2026-47242)

    * net-imap: rubygem-net-imap: Net::IMAP: Denial of Service via malformed command input (CVE-2026-47241)

    Bug Fix(es) and Enhancement(s):

    * ruby:4.0/ruby: Rebase to the latest Ruby 4.0 release [rhel-9.8.z] (JIRA:Rocky Linux-211301)

Tenable has extracted the preceding description block directly from the RockyLinux security advisory.

Note that Nessus has not tested for these issues but has instead relied only on the application's self-reported version number.

The remote MiracleLinux 9 host has packages installed that are affected by multiple vulnerabilities as referenced in the AXSA:2026-1647:01 advisory.

    * zlib: zlib: Memory corruption via buffer overflow in Zlib::GzipReader (CVE-2026-27820)
      * net-imap: Net::IMAP: Arbitrary IMAP command injection via CRLF sequences in unvalidated input     (CVE-2026-42257)
      * ruby/net-imap: ruby: Net::IMAP: Denial of Service via large iteration count in SCRAM authentication     (CVE-2026-42256)
      * net-imap: Net::IMAP: Command injection via non-synchronizing literals (CVE-2026-47240)
      * net-imap: Net::IMAP: Arbitrary IMAP command injection due to improper input validation     (CVE-2026-47242)
      * net-imap: rubygem-net-imap: Net::IMAP: Denial of Service via malformed command input (CVE-2026-47241)

Tenable has extracted the preceding description block directly from the MiracleLinux security advisory.

Note that Nessus has not tested for these issues but has instead relied only on the application's self-reported version number.

The remote Oracle Linux 10 host has packages installed that are affected by multiple vulnerabilities as referenced in the ELSA-2026-50778 advisory.

    [3.3.12-14]
    - Upgrade to Ruby 3.3.12.
      Resolves: RHEL-211300       Resolves: RHEL-193659

Tenable has extracted the preceding description block directly from the Oracle Linux security advisory.

Note that Nessus has not tested for these issues but has instead relied only on the application's self-reported version number.

The remote Oracle Linux 10 host has packages installed that are affected by multiple vulnerabilities as referenced in the ELSA-2026-50773 advisory.

    [4.0.6-36]
    - Upgrade to Ruby 4.0.6.
      Resolves: RHEL-211310       Resolves: RHEL-193660

Tenable has extracted the preceding description block directly from the Oracle Linux security advisory.

Note that Nessus has not tested for these issues but has instead relied only on the application's self-reported version number.

The remote Oracle Linux 8 host has packages installed that are affected by multiple vulnerabilities as referenced in the ELSA-2026-50728 advisory.

    ruby     [3.3.12-8]
    - Upgrade to Ruby 3.3.12.
      Resolves: RHEL-170929       Resolves: RHEL-193664

    rubygem-abrt     rubygem-mysql2     rubygem-pg

Tenable has extracted the preceding description block directly from the Oracle Linux security advisory.

Note that Nessus has not tested for these issues but has instead relied only on the application's self-reported version number.

The remote Oracle Linux 9 host has packages installed that are affected by multiple vulnerabilities as referenced in the ELSA-2026-50827 advisory.

    ruby     [4.0.6-34]
    - Upgrade to Ruby 4.0.6.
      Resolves: RHEL-211301       Resolves: RHEL-193663

    rubygem-mysql2     [0.5.7-1]
    - Upgrade to mysql2 0.5.7.
      Related: RHEL-142278

    [0.5.5-3]
    - Disable tests on the 32bit platforms ix86.
      Related: RHEL-80222

    [0.5.5-2]
    - Adapt tests to openssl 3.2       Resolves: RHEL-80222

    rubygem-pg     [1.6.3-1]
    - Upgrade to pg 1.6.3       Related: RHEL-142278

Tenable has extracted the preceding description block directly from the Oracle Linux security advisory.

Note that Nessus has not tested for these issues but has instead relied only on the application's self-reported version number.

The remote Oracle Linux 9 host has packages installed that are affected by multiple vulnerabilities as referenced in the ELSA-2026-50828 advisory.

    ruby     [3.3.12-8]
    - Upgrade to Ruby 3.3.12.
      Resolves: RHEL-171335       Resolves: RHEL-193665

    rubygem-mysql2     [0.5.5-3]
    - Disable tests on the 32bit platforms ix86.
      Related: RHEL-80222

    [0.5.5-2]
    - Adapt tests to openssl 3.2       Resolves: RHEL-80222

    [0.5.5-1]
    - Upgrade to mysql2 0.5.5.
      Related: RHEL-17089

    rubygem-pg     [-1.5.4-2]
    - Fix encoding issue in spec suite.
      Resolves: RHEL-159199

Tenable has extracted the preceding description block directly from the Oracle Linux security advisory.

Note that Nessus has not tested for these issues but has instead relied only on the application's self-reported version number.

The remote MiracleLinux 8 host has packages installed that are affected by multiple vulnerabilities as referenced in the AXSA:2026-1503:01 advisory.

    * zlib: zlib: Memory corruption via buffer overflow in Zlib::GzipReader (CVE-2026-27820)
      * net-imap: Net::IMAP: Arbitrary IMAP command injection via CRLF sequences in unvalidated input     (CVE-2026-42257)
      * ruby/net-imap: ruby: Net::IMAP: Denial of Service via large iteration count in SCRAM authentication     (CVE-2026-42256)
      * net-imap: Net::IMAP: Command injection via non-synchronizing literals (CVE-2026-47240)
      * net-imap: Net::IMAP: Arbitrary IMAP command injection due to improper input validation     (CVE-2026-47242)
      * net-imap: rubygem-net-imap: Net::IMAP: Denial of Service via malformed command input (CVE-2026-47241)

Tenable has extracted the preceding description block directly from the MiracleLinux security advisory.

Note that Nessus has not tested for these issues but has instead relied only on the application's self-reported version number.

The remote Debian 11 host has packages installed that are affected by multiple vulnerabilities as referenced in the dla-4716 advisory.

    - -------------------------------------------------------------------------     Debian LTS Advisory DLA-4716-1                debian-lts@lists.debian.org     https://www.debian.org/lts/security/                          Abhijith PA     August 04, 2026                               https://wiki.debian.org/LTS
    - -------------------------------------------------------------------------

    Package        : ruby2.7     Version        : 2.7.4-1+deb11u6 $bookworm_VERSION     CVE ID         : CVE-2025-24294 CVE-2025-61594 CVE-2026-27820                      CVE-2026-41316


    Ruby a popular language was affected by multiple vulnerabilities

    CVE-2025-24294

        The vulnerability is caused by an insufficient check on the length         of a decompressed domain name within a DNS packet. An attacker can         craft a malicious DNS packet containing a highly compressed domain         name. When the resolv library parses such a packet, the name         decompression process consumes a large amount of CPU resources, as         the library does not limit the resulting length of the name. This         resource consumption can cause the application thread to become         unresponsive, resulting in a Denial of Service condition.

    CVE-2025-61594

         Using the + operator to combine URIs, sensitive information like          passwords from the original URI can be leaked, violating RFC3986          and making applications vulnerable to credential exposure. URI is          a module providing classes to handle Uniform Resource          Identifiers.

    CVE-2026-27820

        A buffer overflow vulnerability in the Zlib::GzipReader. The         zstream_buffer_ungets function prepends caller-provided bytes         ahead of previously produced output but fails to guarantee the         backing Ruby string has enough capacity before the memmove shifts         the existing data. This can lead to memory corruption when the         buffer length exceeds capacity.

    CVE-2026-41316

        A deserialization vulnerability exists in ERB. Any Ruby         application that calls Marshal.load on untrusted data AND has both         erb and activesupport loaded is vulnerable to arbitrary code         execution.

    For Debian 11 bullseye, these problems have been fixed in version     2.7.4-1+deb11u6.

    We recommend that you upgrade your ruby2.7 packages.

    For the detailed security status of ruby2.7 please refer to     its security tracker page at:
    https://security-tracker.debian.org/tracker/ruby2.7

    Further information about Debian LTS security advisories, how to apply     these updates to your system and frequently asked questions can be     found at: https://wiki.debian.org/LTS

Tenable has extracted the preceding description block directly from the Debian security advisory.

Note that Nessus has not tested for these issues but has instead relied only on the application's self-reported version number.

The remote Ubuntu 16.04 LTS host has packages installed that are affected by multiple vulnerabilities as referenced in the USN-8556-1 advisory.

    It was discovered that the Net::IMAP client in Ruby did not properly sanitize Symbol arguments passed to     IMAP commands. A remote attacker controlling a malicious IMAP server, or able to influence command     arguments, could use this to inject arbitrary IMAP commands via CRLF sequences. (CVE-2026-42258)

    It was discovered that the Zlib::GzipReader in Ruby did not correctly ensure sufficient buffer capacity in     the zstream_buffer_ungets function. An attacker could use this to craft a gzip stream that, when     processed, could cause a buffer overflow, resulting in memory corruption and possibly arbitrary code     execution. (CVE-2026-27820)

Tenable has extracted the preceding description block directly from the Ubuntu security advisory.

Note that Nessus has not tested for these issues but has instead relied only on the application's self-reported version number.

It is, therefore, affected by multiple vulnerabilities as referenced in the ALAS2023-2026-1807 advisory.

    zlib is a Ruby interface for the zlib compression/decompression library. Versions 3.0.0 and below, 3.1.0,     3.1.1, 3.2.0 and 3.2.1 contain a buffer overflow vulnerability in the Zlib::GzipReader. The     zstream_buffer_ungets function prepends caller-provided bytes ahead of previously produced output but     fails to guarantee the backing Ruby string has enough capacity before the memmove shifts the existing     data. This can lead to memory corruption when the buffer length exceeds capacity. This issue has been     fixed in versions 3.0.1, 3.1.2 and 3.2.3. (CVE-2026-27820)

    Net::IMAP implements Internet Message Access Protocol (IMAP) client functionality in Ruby. Prior to     versions 0.4.24, 0.5.14, and 0.6.4, Net::IMAP::ResponseReader has quadratic time complexity when reading     large responses containing many string literals. A hostile server can send responses which are crafted to     exhaust the client's CPU for a denial of service attack. This issue has been patched in versions 0.4.24,     0.5.14, and 0.6.4. (CVE-2026-42245)

    Net::IMAP implements Internet Message Access Protocol (IMAP) client functionality in Ruby. Prior to     versions 0.3.10, 0.4.24, 0.5.14, and 0.6.4, a man-in-the-middle attacker can cause Net::IMAP#starttls to     return successfully, without starting TLS. This issue has been patched in versions 0.3.10, 0.4.24,     0.5.14, and 0.6.4. (CVE-2026-42246)

    Net::IMAP implements Internet Message Access Protocol (IMAP) client functionality in Ruby. From versions     0.4.0 to before 0.4.24, 0.5.0 to before 0.5.14, and 0.6.0 to before 0.6.4, when authenticating a     connection with SCRAM-SHA1 or SCRAM-SHA256, a hostile server can perform a computational denial-of-service     attack on the client process by sending a big iteration count value. This issue has been patched in     versions 0.4.24, 0.5.14, and 0.6.4. (CVE-2026-42256)

    Net::IMAP implements Internet Message Access Protocol (IMAP) client functionality in Ruby. Prior to     versions 0.4.24, 0.5.14, and 0.6.4, several Net::IMAP commands accept a raw string argument that is sent     to the server without validation or escaping. If this string is derived from user-controlled input, it may     contain contain CRLF sequences, which an attacker can use to inject arbitrary IMAP commands. This issue     has been patched in versions 0.4.24, 0.5.14, and 0.6.4. (CVE-2026-42257)

    Net::IMAP implements Internet Message Access Protocol (IMAP) client functionality in Ruby. Prior to     versions 0.4.24, 0.5.14, and 0.6.4, symbol arguments to commands are vulnerable to a CRLF Injection / IMAP     Command injection via Symbol arguments passed to IMAP commands. This issue has been patched in versions     0.4.24, 0.5.14, and 0.6.4. (CVE-2026-42258)

Tenable has extracted the preceding description block directly from the tested product security advisory.

Note that Nessus has not tested for these issues but has instead relied only on the application's self-reported version number.

The Linux/Unix host has one or more packages installed that are impacted by a vulnerability without a vendor supplied patch available.

  - zlib is a Ruby interface for the zlib compression/decompression library. Versions 3.0.0 and below, 3.1.0,     3.1.1, 3.2.0 and 3.2.1 contain a buffer overflow vulnerability in the Zlib::GzipReader. The     zstream_buffer_ungets function prepends caller-provided bytes ahead of previously produced output but     fails to guarantee the backing Ruby string has enough capacity before the memmove shifts the existing     data. This can lead to memory corruption when the buffer length exceeds capacity. This issue has been     fixed in versions 3.0.1, 3.1.2 and 3.2.3. (CVE-2026-27820)

Note that Nessus relies on the presence of the package as reported by the vendor.

The remote SUSE Linux SLED15 / SLED_SAP15 / SLES15 / SLES_SAP15 host has packages installed that are affected by multiple vulnerabilities as referenced in the SUSE-SU-2026:1066-1 advisory.

    - CVE-2024-49761: ReDoS vulnerability in REXML gem (bsc#1232440 bsc#1232441).
    - CVE-2025-58767: denial of service when parsing XML containing multiple XML declarations (bsc#1250016).
    - CVE-2026-27820: insufficient checks in `zstream_buffer_ungets` can lead to a buffer overflow     (bsc#1259239).

Tenable has extracted the preceding description block directly from the SUSE security advisory.

Note that Nessus has not tested for these issues but has instead relied only on the application's self-reported version number.

There are packages installed that are affected by a vulnerability referenced in the following CVE:

  - zlib is a Ruby interface for the zlib compression/decompression library. Versions 3.0.0 and below, 3.1.0,
    3.1.1, 3.2.0 and 3.2.1 contain a buffer overflow vulnerability in the Zlib::GzipReader. The
    zstream_buffer_ungets function prepends caller-provided bytes ahead of previously produced output but
    fails to guarantee the backing Ruby string has enough capacity before the memmove shifts the existing
    data. This can lead to memory corruption when the buffer length exceeds capacity. This issue has been
    fixed in versions 3.0.1, 3.1.2 and 3.2.3. (CVE-2026-27820)

ID	Name	Product	Family	Type	Severity
341076	MiracleLinux 9 : ruby:4.0 (AXSA:2026-1667:01)	Nessus	Miracle Linux Local Security Checks	Local	medium
341008	RockyLinux 8 : ruby:3.3 (RLSA-2026:50728)	Nessus	Rocky Linux Local Security Checks	Local	medium
341007	RockyLinux 10 : ruby (RLSA-2026:50778)	Nessus	Rocky Linux Local Security Checks	Local	medium
341006	RockyLinux 10 : ruby4.0 (RLSA-2026:50773)	Nessus	Rocky Linux Local Security Checks	Local	medium
341005	RockyLinux 9 : ruby:3.3 (RLSA-2026:50828)	Nessus	Rocky Linux Local Security Checks	Local	medium
341004	RockyLinux 9 : ruby:4.0 (RLSA-2026:50827)	Nessus	Rocky Linux Local Security Checks	Local	medium
339405	MiracleLinux 9 : ruby:3.3 (AXSA:2026-1647:01)	Nessus	Miracle Linux Local Security Checks	Local	medium
335471	Oracle Linux 10 : ruby (ELSA-2026-50778)	Nessus	Oracle Linux Local Security Checks	Local	medium
335469	Oracle Linux 10 : ruby4.0 (ELSA-2026-50773)	Nessus	Oracle Linux Local Security Checks	Local	medium
334429	Oracle Linux 8 : ruby:3.3 (ELSA-2026-50728)	Nessus	Oracle Linux Local Security Checks	Local	medium
334161	Oracle Linux 9 : ruby:4.0 (ELSA-2026-50827)	Nessus	Oracle Linux Local Security Checks	Local	medium
334141	Oracle Linux 9 : ruby:3.3 (ELSA-2026-50828)	Nessus	Oracle Linux Local Security Checks	Local	medium
333609	MiracleLinux 8 : ruby:3.3 (AXSA:2026-1503:01)	Nessus	Miracle Linux Local Security Checks	Local	medium
331823	Debian dla-4716 : libruby2.7 - security update	Nessus	Debian Local Security Checks	Local	medium
327617	Ubuntu 16.04 LTS : Ruby vulnerabilities (USN-8556-1)	Nessus	Ubuntu Local Security Checks	Local	medium
319837	Amazon Linux 2023 : ruby3.4, ruby3.4-bundled-gems, ruby3.4-default-gems (ALAS2023-2026-1807)	Nessus	Amazon Linux Local Security Checks	Local	high
306840	Linux Distros Unpatched Vulnerability : CVE-2026-27820	Nessus	Misc.	Local	medium
303945	SUSE SLED15 / SLES15 Security Update : ruby2.5 (SUSE-SU-2026:1066-1)	Nessus	SuSE Local Security Checks	Local	high
438901	Alpine: multiple ruby packages: security update to 3.4.9-r0	Tenable Cloud Security	Alpine Linux Local Security Checks	Local	medium
438901	Alpine: multiple ruby packages: security update to 3.4.9-r0	Tenable Self-Hosted Container Security	Alpine Linux Local Security Checks	Local	medium

Detections

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CVE-2026-27820

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Tenable Plugins

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