Vulnerability Description
In Exim before 4.99.2, when utf8 operators are enabled, there is an out-of-bounds read if large UTF-8 trailing characters are present (malformed UTF-8 header data). Information might be divulged within an error message produced during handling of an unrelated e-mail message.
CVSS Score
LOW
Affected Products
| Vendor | Product | Versions |
|---|---|---|
| Exim | Exim | < 4.99.2 |
Related Weaknesses (CWE)
References
- https://code.exim.org/exim/exim/commit/f2570bde16fb4d4a1242ff363a4c4eecf6372efcPatch
- https://exim.org/static/doc/security/CVE-2026-40686.txtBroken Link
- https://exim.org/static/doc/security/cve-2026-04.1/CVE2026-40686.assessmentVendor Advisory
- https://www.openwall.com/lists/oss-security/2026/04/30/21Mailing ListThird Party Advisory
FAQ
What is CVE-2026-40686?
CVE-2026-40686 is a vulnerability with a CVSS score of 3.7 (LOW). In Exim before 4.99.2, when utf8 operators are enabled, there is an out-of-bounds read if large UTF-8 trailing characters are present (malformed UTF-8 header data). Information might be divulged withi...
How severe is CVE-2026-40686?
CVE-2026-40686 has been rated LOW with a CVSS base score of 3.7/10. Review the CVSS metrics above for detailed severity breakdown.
Is there a patch for CVE-2026-40686?
Check the references section above for vendor advisories and patch information. Affected products include: Exim Exim.