Vulnerability 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 Score
5.9
MEDIUM
CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:H
Affected Products
| Vendor | Product | Versions |
|---|---|---|
| Exim | Exim | < 4.99.2 |
Related Weaknesses (CWE)
References
- https://code.exim.org/exim/exim/commit/628bbaca7672748d941a12e7cd5f0122a4e18c81Patch
- https://exim.org/static/doc/security/CVE-2026-40684.txtBroken Link
- https://exim.org/static/doc/security/cve-2026-04.1/CVE2026-40684.assessmentVendor Advisory
- https://www.openwall.com/lists/oss-security/2026/04/30/21Mailing ListThird Party Advisory
- http://www.openwall.com/lists/oss-security/2026/05/01/11
FAQ
What is CVE-2026-40684?
CVE-2026-40684 is a vulnerability with a CVSS score of 5.9 (MEDIUM). 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 ...
How severe is CVE-2026-40684?
CVE-2026-40684 has been rated MEDIUM with a CVSS base score of 5.9/10. Review the CVSS metrics above for detailed severity breakdown.
Is there a patch for CVE-2026-40684?
Check the references section above for vendor advisories and patch information. Affected products include: Exim Exim.