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CVE-2026-40686VulnerabilityPublished

In Exim before 4.99.2, when utf8 operators are enabled, there is an out-of-bounds read if large UTF-8 trailing

Source GCVE Database

0
Authoritative record:CVE-2026-40686· Low 3.7

Not known to be exploited · CVSS 3.7 Low.

Data as of 27 Oct 2026, 00:35 UTC

CVSS 3.1 base score
3.7Low
How severe the flaw is on the 0–10 CVSS scale.
Affects
Exim before 4.99.2
CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:L/I:N/A:N

Exploitation evidence

  1. Disclosed: evidence found.

    CVE published 30 Apr 2026

  2. Detectable: no evidence on record.

    No public nuclei template indexed

  3. Weaponised: no evidence on record.

    No public exploit code indexed in Metasploit or Exploit-DB

  4. Exploited in the wild: no evidence on record.

    Not in CISA KEV and no source reports exploitation

  5. Observed by OffSeq Mirage: no evidence on record.

    No attack traffic recorded by OffSeq Mirage sensors

A missing step is not evidence of safety. Sources: cve.org (opens in a new tab), the Metasploit, Exploit-DB and nuclei-templates index as of 26 Oct 2026.

What to do

AI-suggested

Until an official fix is available, consider disabling UTF-8 operators if feasible to reduce exposure. Monitor vendor communications for updates and apply patches promptly once released.

Description

A vulnerability in Exim versions before 4.99.2 exists when UTF-8 operators are enabled. This flaw causes an out-of-bounds read if large malformed UTF-8 trailing characters are present in email headers. The issue may lead to information disclosure through error messages generated during the processing of unrelated emails.

References

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