CVE-2026-40686

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.

PUBLISHED Reserved 2026-04-14 | Published 2026-04-30 | Updated 2026-05-01 | Assigner mitre

Problem types

CWE-125 Out-of-bounds Read

Product status

References

www.openwall.com/lists/oss-security/2026/04/30/21

exim.org/.../security/cve-2026-04.1/CVE2026-40686.assessment

code.exim.org/...it/f2570bde16fb4d4a1242ff363a4c4eecf6372efc

exim.org/static/doc/security/CVE-2026-40686.txt

cve.org (CVE-2026-40686)

nvd.nist.gov (CVE-2026-40686)

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