CVE-2026-40686
8Vexday Risk Score
No sign of exploitation. No public exploitation artifact known so far.
ssvc Trackcvss 3.7epss 0.2%
exploitation probability
0.2%top 84% of all CVEs
observed exploitation
nono source reports it
In short
Exim mail server can accidentally leak information when processing broken UTF-8 characters in email headers if a specific feature is enabled. An attacker could trigger an error message that reveals sensitive data from other emails.
Technical detail
An out-of-bounds read vulnerability exists in Exim <4.99.2 when utf8 operators are enabled, triggered by malformed UTF-8 sequences in email headers. The vulnerability requires the utf8 feature to be active and allows information disclosure through error messages generated during unrelated message processing; attack vector is network-based via crafted email headers.
Summary generated and translated by AI from the official 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:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:L/I:N/A:N
Affected products
Exim · Exim