Exim 4.88 before 4.99.4, in some proxy configurations, mishandles certain short payloads, leading to disclosure of uninitialized stack memory values to a client.

The remote Fedora 44 host has a package installed that is affected by a vulnerability as referenced in the FEDORA-2026-78bf093219 advisory.

    This is an update fixing a pre-authentication information disclosure (CVE-2026-48840).


Tenable has extracted the preceding description block directly from the Fedora 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 Fedora 43 host has a package installed that is affected by a vulnerability as referenced in the FEDORA-2026-71b1e9b455 advisory.

    This is an update fixing a pre-authentication information disclosure (CVE-2026-48840).


Tenable has extracted the preceding description block directly from the Fedora 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 Debian 11 host has packages installed that are affected by a vulnerability as referenced in the dla-4615 advisory.

    - -------------------------------------------------------------------------     Debian LTS Advisory DLA-4615-1                debian-lts@lists.debian.org     https://www.debian.org/lts/security/                    Thorsten Alteholz     June 05, 2026                                 https://wiki.debian.org/LTS
    - -------------------------------------------------------------------------

    Package        : exim4     Version        : 4.94.2-7+deb11u6     CVE ID         : CVE-2026-48840


    Warisjeet Singh discovered that Exim, a mail transport agent, does not     properly handle PROXY frames whose declared payload length is too short     for the claimed address family, which may result in information     disclosure in configurations with SUPPORT_PROXY and 'host_proxy' set.


    For Debian 11 bullseye, this problem has been fixed in version     4.94.2-7+deb11u6.

    We recommend that you upgrade your exim4 packages.

    For the detailed security status of exim4 please refer to     its security tracker page at:
    https://security-tracker.debian.org/tracker/exim4

    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 this issue but has instead relied only on the application's self-reported version number.

According to its banner, the version of Exim running on the remote host is 4.88 or later but prior to 4.99.4. It is, therefore, potentially affected by an information disclosure vulnerability.

  - Exim 4.88 before 4.99.4, in some proxy configurations, mishandles certain short payloads, leading to disclosure     of uninitialized stack memory values to a client. (CVE-2026-48840)

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

The remote Ubuntu 14.04 LTS / 16.04 LTS / 18.04 LTS / 20.04 LTS host has packages installed that are affected by multiple vulnerabilities as referenced in the USN-8382-1 advisory.

    Timo Longin discovered that Exim incorrectly handled certain SMTP messages in PIPELINING/CHUNKING     configurations. A remote attacker could possibly use this issue to perform SMTP smuggling. This issue only     affected Ubuntu 14.04 LTS. (CVE-2023-51766)

    It was discovered that Exim incorrectly handled certain malformed JSON data in headers. A remote attacker     could possibly use this issue to crash Exim, resulting in a denial of service, or execute arbitrary code.
    This issue only affected Ubuntu 20.04 LTS. (CVE-2026-40685)

    It was discovered that Exim incorrectly handled certain malformed UTF-8 headers. A remote attacker could     possibly use this issue to obtain sensitive information. This issue only affected Ubuntu 20.04 LTS.
    (CVE-2026-40686)

    It was discovered that Exim incorrectly handled certain SPA resources. A remote attacker could possibly     use this issue to crash Exim, resulting in a denial of service, or obtain sensitive information. This     issue only affected Ubuntu 20.04 LTS. (CVE-2026-40687)

    It was discovered that Exim incorrectly handled certain CHUNKING transfers in some GnuTLS configurations.
    A remote attacker could possibly use this issue to crash Exim, resulting in a denial of service, or     execute arbitrary code. This issue only affected Ubuntu 20.04 LTS. (CVE-2026-45185)

    Warisjeet Singh discovered that Exim incorrectly handled certain proxy connections in builds with proxy     support enabled. A remote attacker could possibly use this issue to obtain sensitive information. This     issue only affected Ubuntu 16.04 LTS, Ubuntu 18.04 LTS, and Ubuntu 20.04 LTS. (CVE-2026-48840)

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 remote Ubuntu 22.04 LTS / 24.04 LTS / 25.10 / 26.04 LTS host has packages installed that are affected by a vulnerability as referenced in the USN-8353-1 advisory.

    Warisjeet Singh discovered that Exim with SUPPORT_PROXY enabled did not properly handle memory before SMTP     authentication. A remote attacker could possibly use this issue to obtain sensitive information.

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.

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

  - Exim 4.88 before 4.99.4, in some proxy configurations, mishandles certain short payloads, leading to
    disclosure of uninitialized stack memory values to a client. (CVE-2026-48840)

The remote Debian 12 / 13 host has packages installed that are affected by a vulnerability as referenced in the dsa-6309 advisory.

    - -------------------------------------------------------------------------     Debian Security Advisory DSA-6309-1                   security@debian.org     https://www.debian.org/security/                     Salvatore Bonaccorso     May 29, 2026                          https://www.debian.org/security/faq
    - -------------------------------------------------------------------------

    Package        : exim4     CVE ID         : CVE-2026-48840

    Warisjeet Singh discovered that Exim, a mail transport agent, does not     properly handle PROXY frames whose declared payload length is too short     for the claimed address family, which may result in information     disclosure in configurations with SUPPORT_PROXY and 'host_proxy' set.

    For the oldstable distribution (bookworm), this problem has been fixed     in version 4.96-15+deb12u10.

    For the stable distribution (trixie), this problem has been fixed in     version 4.98.2-1+deb13u3.

    We recommend that you upgrade your exim4 packages.

    For the detailed security status of exim4 please refer to its security     tracker page at:
    https://security-tracker.debian.org/tracker/exim4

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

    Mailing list: debian-security-announce@lists.debian.org

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

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
320209	Fedora 44 : exim (2026-78bf093219)	Nessus	Fedora Local Security Checks	medium
320208	Fedora 43 : exim (2026-71b1e9b455)	Nessus	Fedora Local Security Checks	medium
318796	Debian dla-4615 : exim4 - security update	Nessus	Debian Local Security Checks	medium
318666	Exim 4.88 < 4.99.4 Information Disclosure	Nessus	SMTP problems	medium
318625	Ubuntu 14.04 LTS / 16.04 LTS / 18.04 LTS / 20.04 LTS : Exim vulnerabilities (USN-8382-1)	Nessus	Ubuntu Local Security Checks	critical
318266	Ubuntu 22.04 LTS / 24.04 LTS / 25.10 / 26.04 LTS : Exim vulnerability (USN-8353-1)	Nessus	Ubuntu Local Security Checks	medium
442553	Alpine: multiple exim packages: security update to 4.98.4-r0	Tenable Cloud Security	Alpine Linux Local Security Checks	medium
442553	Alpine: multiple exim packages: security update to 4.98.4-r0	Tenable Self-Hosted Container Security	Alpine Linux Local Security Checks	medium
317932	Debian dsa-6309 : exim4 - security update	Nessus	Debian Local Security Checks	medium

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CVE-2026-48840

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