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.
Affected products
exim: exim
References4
- exim.org/static/doc/security/cve-2026-04.1/CVE2026-40686.assess… Vendor Advisory
- code.exim.org/exim/exim/commit/f2570bde16fb4d4a1242ff363a4c4eec… Patch
- exim.org/static/doc/security/CVE-2026-40686.txt Broken Link
- www.openwall.com/lists/oss-security/2026/04/30/21 Mailing ListThird Party Advisory
Metrics
- CVSS 3.1
-
5.3
MEDIUM
Score source: NVD
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:N/A:N - EPSS — exploit probability
- 0% percentile: 16 · as of 13 November 2026
- CWE
- CWE-125
Could this be exploited in your environment?
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