PT-2026-36195 · Exim+1 · Exim+1

Bernard Quatermass · CVE-2026-40684 · Published 2026-04-30 · Updated 2026-07-29

Positive Technologies (AI Summary)

CVSS v3.1

7.5

High

Base vector

AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

Name of the Vulnerable Software and Affected Versions Exim versions prior to 4.99.2

Description An issue exists on systems using musl libc (excluding glibc) where an attacker can cause a connection instance to crash. This occurs when the software processes malformed DNS data within PTR records, resulting from an oddity in octal printing within the dn expand() function.

Recommendations Update to version 4.99.2.

Fix

DoS

Weakness Enumeration

CWE-684

Related Identifiers

CVE-2026-40684

Affected Products

Exim

Red Os

References · 19

• https://nvd.nist.gov/vuln/detail/CVE-2026-40684 · Security Note
• https://exim.org/static/doc/security/cve-2026-04.1/CVE2026-40684.assessment · Vendor Advisory
• https://security-tracker.debian.org/tracker/CVE-2026-40684 · Vendor Advisory
• https://code.exim.org/exim/exim/commit/628bbaca7672748d941a12e7cd5f0122a4e18c81 · Patch
• https://osv.dev/vulnerability/DEBIAN-CVE-2026-40684 · Vendor Advisory
• https://openwall.com/lists/oss-security/2026/04/30/21 · Note
• https://redos.red-soft.ru/support/secure/uyazvimosti/support/secure/uyazvimosti/uyazvimost-exim-cve-2026-40684-7.3 · Note
• https://twitter.com/VulmonFeeds/status/2050002945853309168 · Twitter Post
• https://t.me/cveNotify/161678 · Telegram Post
• https://twitter.com/dnsaudit/status/2050653888357789905 · Twitter Post
• https://exim.org/static/doc/security/CVE-2026-40684.txt · Note
• http://openwall.com/lists/oss-security/2026/05/01/11 · Note
• https://reddit.com/r/cpanel/comments/1t3qd0y/first_cpanel_then_kernel_and_now_exim · Reddit Post
• https://twitter.com/CVEnew/status/2049970638929175027 · Twitter Post
• https://twitter.com/infoflowcloud/status/2049972642497585165 · Twitter Post