CVE-2026-40684
highIn 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.
Vendor / product: 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.
CVSS
7.5
7.5 (CVSS v3.1)
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H Severity source: NVD CVSS v3.1 (nvd@nist.gov)
Timeline (UTC)
Published: 2026-04-30 22:16
Modified: 2026-11-11 21:10
NVD status: Modified
Last synced 5 hours ago
Verified against the source API 2026-11-11 21:11 UTC
Exploitation
Not listed in CISA KEV (as of last catalog sync)
Absence from KEV does not mean a CVE is not exploited. Exploitation status: unknown (no authoritative evidence in our sources).
Affected products
exim / exim <4.99.2
Weakness classification (CWE)
Source: NVD / CISA. “NVD-CWE-Other” and “NVD-CWE-noinfo” mean NVD could not assign a specific weakness.
Mitigation & advisories
Patch / mitigation: https://code.exim.org/exim/exim/commit/628bbaca7672748d941a12e7cd5f0122a4e18c81
References
- https://code.exim.org/exim/exim/commit/628bbaca7672748d941a12e7cd5f0122a4e18c81 cve@mitre.org
- https://exim.org/static/doc/security/CVE-2026-40684.txt cve@mitre.org
- https://exim.org/static/doc/security/cve-2026-04.1/CVE2026-40684.assessment cve@mitre.org
- https://www.openwall.com/lists/oss-security/2026/04/30/21 cve@mitre.org
- http://www.openwall.com/lists/oss-security/2026/05/01/11 af854a3a-2127-422b-91ae-364da2661108
Data sources
NVD CVE API 2.0 — fetched 2026-11-11 21:11 UTC · record ↗