In Exim before 4.99.2, on systems using musl libc (not glibc), an attacker can crash the connection instance when malformed DNS data is present in PTR records. This is caused by a dn_expand oddity in octal printing.

The remote host is affected by the vulnerability described in GLSA-202608-07 (Exim: Multiple Vulnerabilities)

    Multiple vulnerabilities have been discovered in Exim. Please review the CVE identifiers referenced below     for details.

Tenable has extracted the preceding description block directly from the Gentoo 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 Debian 12 / 13 host has packages installed that are affected by multiple vulnerabilities as referenced in the dsa-6265 advisory.

    - -------------------------------------------------------------------------     Debian Security Advisory DSA-6265-1                   security@debian.org     https://www.debian.org/security/                     Salvatore Bonaccorso     May 12, 2026                          https://www.debian.org/security/faq
    - -------------------------------------------------------------------------

    Package        : exim4     CVE ID         : CVE-2026-40684 CVE-2026-40685 CVE-2026-40686 CVE-2026-40687

    Several vulnerabilities were discovered in the Exim mail transport     agent, which may result in remote code execution, denial of service or     an information leak.

    For the oldstable distribution (bookworm), these problems have been fixed     in version 4.96-15+deb12u9.

    For the stable distribution (trixie), these problems have been fixed in     version 4.98.2-1+deb13u2.

    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 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.

  - In Exim before 4.99.2, on systems using musl libc (not glibc), an attacker can crash the connection     instance when malformed DNS data is present in PTR records. This is caused by a dn_expand oddity in octal     printing. (CVE-2026-40684)

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

ID	Name	Product	Family	Type	Severity
335323	GLSA-202608-07 : Exim: Multiple Vulnerabilities	Nessus	Gentoo Local Security Checks	Local	critical
314336	Debian dsa-6265 : exim4 - security update	Nessus	Debian Local Security Checks	Local	critical
311146	Linux Distros Unpatched Vulnerability : CVE-2026-40684	Nessus	Misc.	Local	high

Detections

Analytics

CVE-2026-40684

high

Tenable Plugins

critical

critical

high