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Vulnerability record · CVE-2026-40684 · published 30 April 2026

CVE-2026-40684: Exim vulnerability

Exim · Exim

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.

7.5 CVSS 3.1 High EPSS 0.61% · top 53.1% CWE-684 · CWE-684
7.5CVSS 3.1 base score
0.61%EPSS exploitation probability, 30 days
NoNot in CISA KEV
1Affected product versions listed by NVD
5References
17 Jun 2026Last modified by NVD

Description

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.

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

Affected products

1 vulnerable configurations from NVD's CPE data, grouped by vendor and product.

References

LinkTags
https://code.exim.org/exim/exim/commit/628bbaca7672748d941a12e7cd5f0122a4e18c81 Patch
https://exim.org/static/doc/security/CVE-2026-40684.txt Broken Link
https://exim.org/static/doc/security/cve-2026-04.1/CVE2026-40684.assessment Vendor Advisory
https://www.openwall.com/lists/oss-security/2026/04/30/21 Mailing ListThird Party Advisory
http://www.openwall.com/lists/oss-security/2026/05/01/11

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Related vulnerabilities

Same products first, then exploited flaws of the same weakness class.

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Source: NIST National Vulnerability Database (record CVE-2026-40684), CISA KEV, FIRST EPSS (scores of 2026-09-26). This page is refreshed as NVD updates the record.