Ruby WEBrick read_header HTTP Request Smuggling Vulnerability. This vulnerability allows remote attackers to smuggle arbitrary HTTP requests on affected installations of Ruby WEBrick. This issue is exploitable when the product is deployed behind an HTTP proxy that fulfills specific conditions. The specific flaw exists within the read_headers method. The issue results from the inconsistent parsing of terminators of HTTP headers. An attacker can leverage this vulnerability to smuggle arbitrary HTTP requests. Was ZDI-CAN-21876.

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

  - Ruby WEBrick read_header HTTP Request Smuggling Vulnerability. This vulnerability allows remote attackers
    to smuggle arbitrary HTTP requests on affected installations of Ruby WEBrick. This issue is exploitable
    when the product is deployed behind an HTTP proxy that fulfills specific conditions. The specific flaw
    exists within the read_headers method. The issue results from the inconsistent parsing of terminators of
    HTTP headers. An attacker can leverage this vulnerability to smuggle arbitrary HTTP requests. Was ZDI-
    CAN-21876. (CVE-2025-6442)

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-2025:4264-1 advisory.

    - CVE-2024-35221: Fixed remote DoS via YAML manifest (bsc#1225905)
    - CVE-2024-47220: Fixed HTTP request smuggling in WEBrick (bsc#1230930)
    - CVE-2024-49761: Fixed ReDOS vulnerability by updating REXML to 3.3.9 (bsc#1232440)
    - CVE-2025-24294: Fixed denial of service (DoS) caused by an insufficient check on the length       of a decompressed domain name within a DNS packet in resolv gem (bsc#1246430)
    - CVE-2025-27219: Fixed denial of service in CGI::Cookie.parse (bsc#1237804)
    - CVE-2025-27220: Fixed ReDoS in CGI::Util#escapeElement (bsc#1237806)
    - CVE-2025-27221: Fixed userinfo leakage in URI#join, URI#merge and URI#+ (bsc#1237805)
    - CVE-2025-6442: Fixed ruby WEBrick read_header HTTP request smuggling vulnerability (bsc#1245254)

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.

According to the versions of the ruby packages installed, the EulerOS installation on the remote host is affected by the following vulnerabilities :

    Ruby WEBrick read_header HTTP Request Smuggling Vulnerability. This vulnerability allows remote attackers     to smuggle arbitrary HTTP requests on affected installations of Ruby WEBrick. This issue is exploitable     when the product is deployed behind an HTTP proxy that fulfills specific conditions.

    The specific flaw exists within the read_headers method. The issue results from the inconsistent parsing     of terminators of HTTP headers. An attacker can leverage this vulnerability to smuggle arbitrary HTTP     requests. Was ZDI-CAN-21876.(CVE-2025-6442)

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

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

The remote host is running a version of macOS / Mac OS X that is 15.x prior to 15.7.2. It is, therefore, affected by multiple vulnerabilities:

  - A memory corruption issue was addressed with improved memory handling. This issue is fixed in watchOS     26.1, iOS 18.7.2 and iPadOS 18.7.2, macOS Tahoe 26.1, visionOS 26.1, tvOS 26.1, macOS Sonoma 14.8.2, macOS     Sequoia 15.7.2, iOS 26.1 and iPadOS 26.1. A malicious application may be able to cause unexpected system     termination or write kernel memory. (CVE-2025-43520)

  - REXML is an XML toolkit for Ruby. The REXML gem before 3.3.6 has a DoS vulnerability when it parses an XML     that has many deep elements that have same local name attributes. If you need to parse untrusted XMLs with     tree parser API like REXML::Document.new, you may be impacted to this vulnerability. If you use other     parser APIs such as stream parser API and SAX2 parser API, this vulnerability is not affected. The REXML     gem 3.3.6 or later include the patch to fix the vulnerability. (CVE-2024-43398)

  - REXML is an XML toolkit for Ruby. The REXML gem before 3.3.9 has a ReDoS vulnerability when it parses an     XML that has many digits between &# and x...; in a hex numeric character reference (&#x...;). This does     not happen with Ruby 3.2 or later. Ruby 3.1 is the only affected maintained Ruby. The REXML gem 3.3.9 or     later include the patch to fix the vulnerability. (CVE-2024-49761)

  - A permissions issue was addressed with improved validation. This issue is fixed in macOS Ventura 13.7.5,     iPadOS 17.7.6, macOS Sequoia 15.4, macOS Sonoma 14.7.5. A shortcut may be able to access files that are     normally inaccessible to the Shortcuts app. (CVE-2025-30465)

  - A race condition was addressed with improved state handling. This issue is fixed in macOS Tahoe 26, macOS     Sequoia 15.7.2. An app may be able to access sensitive user data. (CVE-2025-43292)

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

The remote host is running a version of macOS / Mac OS X that is 26.x prior to 26.1. It is, therefore, affected by multiple vulnerabilities:

  - A memory corruption issue was addressed with improved lock state checking. This issue is fixed in iOS     18.7.2 and iPadOS 18.7.2, iOS 26.1 and iPadOS 26.1, macOS Sequoia 15.7.2, macOS Sonoma 14.8.2, macOS Tahoe     26.1, tvOS 26.1, visionOS 26.1, watchOS 26.1. A malicious application may cause unexpected changes in     memory shared between processes. (CVE-2025-43510)

  - Sudo before 1.9.17p1, when used with a sudoers file that specifies a host that is neither the current host     nor ALL, allows listed users to execute commands on unintended machines. (CVE-2025-32462)

  - REXML is an XML toolkit for Ruby. The REXML gem before 3.3.6 has a DoS vulnerability when it parses an XML     that has many deep elements that have same local name attributes. If you need to parse untrusted XMLs with     tree parser API like REXML::Document.new, you may be impacted to this vulnerability. If you use other     parser APIs such as stream parser API and SAX2 parser API, this vulnerability is not affected. The REXML     gem 3.3.6 or later include the patch to fix the vulnerability. (CVE-2024-43398)

  - REXML is an XML toolkit for Ruby. The REXML gem before 3.3.9 has a ReDoS vulnerability when it parses an     XML that has many digits between &# and x...; in a hex numeric character reference (&#x...;). This does     not happen with Ruby 3.2 or later. Ruby 3.1 is the only affected maintained Ruby. The REXML gem 3.3.9 or     later include the patch to fix the vulnerability. (CVE-2024-49761)

  - A permissions issue was addressed with improved validation. This issue is fixed in iPadOS 17.7.6, macOS     Sequoia 15.4, macOS Sequoia 15.7.2, macOS Sonoma 14.7.5, macOS Sonoma 14.8.2, macOS Tahoe 26.1, macOS     Ventura 13.7.5. A shortcut may be able to access files that are normally inaccessible to the Shortcuts     app. (CVE-2025-30465)

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

The remote host is running a version of macOS / Mac OS X that is 14.x prior to 14.8.2. It is, therefore, affected by multiple vulnerabilities:

  - There exists a vulnerability in SQLite versions before 3.50.2 where the number of aggregate terms could     exceed the number of columns available. This could lead to a memory corruption issue. We recommend     upgrading to version 3.50.2 or above. (CVE-2025-6965)

  - REXML is an XML toolkit for Ruby. The REXML gem before 3.3.6 has a DoS vulnerability when it parses an XML     that has many deep elements that have same local name attributes. If you need to parse untrusted XMLs with     tree parser API like REXML::Document.new, you may be impacted to this vulnerability. If you use other     parser APIs such as stream parser API and SAX2 parser API, this vulnerability is not affected. The REXML     gem 3.3.6 or later include the patch to fix the vulnerability. (CVE-2024-43398)

  - REXML is an XML toolkit for Ruby. The REXML gem before 3.3.9 has a ReDoS vulnerability when it parses an     XML that has many digits between &# and x...; in a hex numeric character reference (&#x...;). This does     not happen with Ruby 3.2 or later. Ruby 3.1 is the only affected maintained Ruby. The REXML gem 3.3.9 or     later include the patch to fix the vulnerability. (CVE-2024-49761)

  - A permissions issue was addressed with improved validation. This issue is fixed in iPadOS 17.7.6, macOS     Sequoia 15.4, macOS Sequoia 15.7.2, macOS Sonoma 14.7.5, macOS Sonoma 14.8.2, macOS Tahoe 26.1, macOS     Ventura 13.7.5. A shortcut may be able to access files that are normally inaccessible to the Shortcuts     app. (CVE-2025-30465)

  - A logging issue was addressed with improved data redaction. This issue is fixed in iOS 18.4 and iPadOS     18.4, macOS Sequoia 15.4, macOS Sonoma 14.8.2, visionOS 2.4. An app may be able to access sensitive user     data. (CVE-2025-31199)

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

The remote Ubuntu 16.04 LTS / 18.04 LTS / 20.04 LTS host has packages installed that are affected by multiple vulnerabilities as referenced in the USN-7840-1 advisory.

    It was discovered that the REXML module bunded into Ruby incorrectly handled parsing XML documents with     repeated instances of certain characters. An attacker could possibly use this issue to cause REXML to     consume excessive resources, leading to a denial of service. Ubuntu 18.04 LTS and Ubuntu 20.04 LTS were     previously addressed in USN-7256-1 and USN-7734-1. This update addresses the issue in Ubuntu 16.04 LTS.
    (CVE-2024-35176)

    It was discovered that the REXML module bunded into Ruby incorrectly handled parsing XML documents with     repeated instances of certain characters. An attacker could possibly use this issue to cause REXML to     consume excessive resources, leading to a denial of service. Ubuntu 20.04 LTS was previously addressed in     USN-7256-1. This update addresses the issue in Ubuntu 16.04 LTS and Ubuntu 18.04 LTS. (CVE-2024-39908,     CVE-2024-41123)

    It was discovered that the REXML module bunded into Ruby incorrectly handled parsing XML documents with     many entity expansions. An attacker could possibly use this issue to cause REXML to consume excessive     resources, leading to a denial of service. Ubuntu 20.04 LTS was previously addressed in USN-7091-2. This     update addresses the issue in Ubuntu 16.04 LTS and Ubuntu 18.04 LTS. (CVE-2024-41946)

    It was discovered that the WEBrick module bundled into Ruby incorrectly handled having both a Content-     Length header and a Transfer-Encoding header. A remote attacker could possibly use this issue to perform a     HTTP request smuggling attack. (CVE-2024-47220)

    It was discovered that the WEBrick module bundled into Ruby incorrectly parsed HTTP headers. In     configurations where the WEBrick module is placed behind an HTTP proxy, a remote attacker could possibly     use this issue to perform an HTTP Request Smuggling attack. (CVE-2025-6442)

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.

The Unity Linux 20 host has a package installed that is affected by a vulnerability as referenced in the UTSA-2025-984790 advisory.

    Ruby WEBrick read_header HTTP Request Smuggling Vulnerability. This vulnerability allows remote attackers     to smuggle arbitrary HTTP requests on affected installations of Ruby WEBrick. This issue is exploitable     when the product is deployed behind an HTTP proxy that fulfills specific conditions.

    The specific flaw exists within the read_headers method. The issue results from the inconsistent parsing     of terminators of HTTP headers. An attacker can leverage this vulnerability to smuggle arbitrary HTTP     requests. Was ZDI-CAN-21876.

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

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

The Unity Linux 20 host has a package installed that is affected by a vulnerability as referenced in the UTSA-2025-984668 advisory.

    Ruby WEBrick read_header HTTP Request Smuggling Vulnerability. This vulnerability allows remote attackers     to smuggle arbitrary HTTP requests on affected installations of Ruby WEBrick. This issue is exploitable     when the product is deployed behind an HTTP proxy that fulfills specific conditions.

    The specific flaw exists within the read_headers method. The issue results from the inconsistent parsing     of terminators of HTTP headers. An attacker can leverage this vulnerability to smuggle arbitrary HTTP     requests. Was ZDI-CAN-21876.

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

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

An update of the rubygem package has been released.

The remote SUSE Linux SLES15 / SLES_SAP15 host has packages installed that are affected by multiple vulnerabilities as referenced in the SUSE-SU-2025:02739-2 advisory.

    - CVE-2025-6442: Fixed read_header HTTP Request Smuggling Vulnerability in WEBrick (bsc#1245254)
    - CVE-2025-27221: Fixed userinfo leakage in URI#join, URI#merge and URI#+ (bsc#1237805)

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.

The remote Ubuntu 22.04 LTS / 24.04 LTS / 25.04 host has a package installed that is affected by a vulnerability as referenced in the USN-7709-1 advisory.

    It was discovered that WEBrick incorrectly parsed HTTP headers. In configurations where WEBrick is placed     behind an HTTP proxy, a remote attacker could possibly use this issue to perform an HTTP Request Smuggling     attack.

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

Note that Nessus has not tested for this issue 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.

  - Ruby WEBrick read_header HTTP Request Smuggling Vulnerability. This vulnerability allows remote attackers     to smuggle arbitrary HTTP requests on affected installations of Ruby WEBrick. This issue is exploitable     when the product is deployed behind an HTTP proxy that fulfills specific conditions. The specific flaw     exists within the read_headers method. The issue results from the inconsistent parsing of terminators of     HTTP headers. An attacker can leverage this vulnerability to smuggle arbitrary HTTP requests. Was ZDI-     CAN-21876. (CVE-2025-6442)

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 / openSUSE 15 host has packages installed that are affected by multiple vulnerabilities as referenced in the SUSE-SU-2025:02739-1 advisory.

    - CVE-2025-6442: Fixed read_header HTTP Request Smuggling Vulnerability in WEBrick (bsc#1245254)
    - CVE-2025-27221: Fixed userinfo leakage in URI#join, URI#merge and URI#+ (bsc#1237805)

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.

It is, therefore, affected by a vulnerability as referenced in the ALAS2023-2025-1115 advisory.

    Ruby WEBrick read_header HTTP Request Smuggling Vulnerability. This vulnerability allows remote attackers     to smuggle arbitrary HTTP requests on affected installations of Ruby WEBrick. This issue is exploitable     when the product is deployed behind an HTTP proxy that fulfills specific conditions.

    The specific flaw exists within the read_headers method. The issue results from the inconsistent parsing     of terminators of HTTP headers. An attacker can leverage this vulnerability to smuggle arbitrary HTTP     requests. Was ZDI-CAN-21876. (CVE-2025-6442)

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

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

The version of ruby installed on the remote host is prior to 2.0.0.648-36. It is, therefore, affected by a vulnerability as referenced in the ALAS2-2025-2931 advisory.

    Ruby WEBrick read_header HTTP Request Smuggling Vulnerability. This vulnerability allows remote attackers     to smuggle arbitrary HTTP requests on affected installations of Ruby WEBrick. This issue is exploitable     when the product is deployed behind an HTTP proxy that fulfills specific conditions.

    The specific flaw exists within the read_headers method. The issue results from the inconsistent parsing     of terminators of HTTP headers. An attacker can leverage this vulnerability to smuggle arbitrary HTTP     requests. Was ZDI-CAN-21876. (CVE-2025-6442)

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

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

The version of ruby / rubygem-webrick installed on the remote CBL Mariner 2.0 host is prior to tested version. It is, therefore, affected by a vulnerability as referenced in the CVE-2025-6442 advisory.

  - Ruby WEBrick read_header HTTP Request Smuggling Vulnerability. This vulnerability allows remote attackers     to smuggle arbitrary HTTP requests on affected installations of Ruby WEBrick. This issue is exploitable     when the product is deployed behind an HTTP proxy that fulfills specific conditions. The specific flaw     exists within the read_headers method. The issue results from the inconsistent parsing of terminators of     HTTP headers. An attacker can leverage this vulnerability to smuggle arbitrary HTTP requests. Was ZDI-     CAN-21876. (CVE-2025-6442)

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

The version of ruby / rubygem-webrick installed on the remote Azure Linux 3.0 host is prior to tested version. It is, therefore, affected by a vulnerability as referenced in the CVE-2025-6442 advisory.

  - Ruby WEBrick read_header HTTP Request Smuggling Vulnerability. This vulnerability allows remote attackers     to smuggle arbitrary HTTP requests on affected installations of Ruby WEBrick. This issue is exploitable     when the product is deployed behind an HTTP proxy that fulfills specific conditions. The specific flaw     exists within the read_headers method. The issue results from the inconsistent parsing of terminators of     HTTP headers. An attacker can leverage this vulnerability to smuggle arbitrary HTTP requests. Was ZDI-     CAN-21876. (CVE-2025-6442)

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

The version of the WEBrick Ruby library installed on the remote host is prior to 1.8.2. It is, therefore, affected by an HTTP request smuggling vulnerability in the read_header. This vulnerability allows remote attackers to smuggle arbitrary HTTP requests on affected installations of Ruby WEBrick. This issue is exploitable when the product is deployed behind an HTTP proxy that fulfills specific conditions. The specific flaw exists within the read_headers method. The issue results from the inconsistent parsing of terminators of HTTP headers. An attacker can leverage this vulnerability to smuggle arbitrary HTTP requests.

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

ID	Name	Product	Family	Severity
437229	SCA: security update for webrick (GHSA-r995-q44h-hr64)	Tenable Cloud Security	SCA Checks	medium
437229	SCA: security update for webrick (GHSA-r995-q44h-hr64)	Tenable Self-Hosted Container Security	SCA Checks	medium
277246	SUSE SLED15: libruby2_5-2_5 / ruby2.5 / ruby2.5-devel / ruby2.5-devel-extra / etc (SUSE-SU-2025:4264-1)	Nessus	SuSE Local Security Checks	high
274957	EulerOS 2.0 SP10 : ruby (EulerOS-SA-2025-2428)	Nessus	Huawei Local Security Checks	medium
274904	EulerOS 2.0 SP10 : ruby (EulerOS-SA-2025-2400)	Nessus	Huawei Local Security Checks	medium
272235	macOS 15.x < 15.7.2 Multiple Vulnerabilities (125635)	Nessus	MacOS X Local Security Checks	high
272228	macOS 26.x < 26.1 Multiple Vulnerabilities (125634)	Nessus	MacOS X Local Security Checks	high
272227	macOS 14.x < 14.8.2 Multiple Vulnerabilities (125636)	Nessus	MacOS X Local Security Checks	high
271850	Ubuntu 16.04 LTS / 18.04 LTS / 20.04 LTS : Ruby vulnerabilities (USN-7840-1)	Nessus	Ubuntu Local Security Checks	medium
267404	Unity Linux 20.1070e Security Update: rubygem-webrick (UTSA-2025-984790)	Nessus	Unity Linux Local Security Checks	medium
267047	Unity Linux 20.1070e Security Update: ruby (UTSA-2025-984668)	Nessus	Unity Linux Local Security Checks	medium
264552	Photon OS 5.0: Rubygem PHSA-2025-5.0-0615	Nessus	PhotonOS Local Security Checks	medium
264551	Photon OS 4.0: Rubygem PHSA-2025-4.0-0867	Nessus	PhotonOS Local Security Checks	medium
260432	SUSE SLES15: libruby2_5-2_5 / ruby2.5 / ruby2.5-devel / ruby2.5-devel-extra / etc (SUSE-SU-2025:02739-2)	Nessus	SuSE Local Security Checks	low
253653	Ubuntu 22.04 LTS / 24.04 LTS / 25.04 : WEBrick vulnerability (USN-7709-1)	Nessus	Ubuntu Local Security Checks	medium
251535	Linux Distros Unpatched Vulnerability : CVE-2025-6442	Nessus	Misc.	medium
246926	SUSE SLED15: libruby2_5-2_5 / ruby2.5 / ruby2.5-devel / ruby2.5-devel-extra / etc (SUSE-SU-2025:02739-1)	Nessus	SuSE Local Security Checks	low
243482	Amazon Linux 2023 : ruby3.2, ruby3.2-bundled-gems, ruby3.2-default-gems (ALAS2023-2025-1115)	Nessus	Amazon Linux Local Security Checks	medium
243248	Amazon Linux 2 : ruby (ALAS-2025-2931)	Nessus	Amazon Linux Local Security Checks	medium
241924	CBL Mariner 2.0 Security Update: ruby / rubygem-webrick (CVE-2025-6442)	Nessus	MarinerOS Local Security Checks	medium
241907	Azure Linux 3.0 Security Update: ruby / rubygem-webrick (CVE-2025-6442)	Nessus	Azure Linux Local Security Checks	medium
240854	Ruby WEBrick < 1.8.2 HTTP Request Smuggling	Nessus	Misc.	medium

Detections

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