CVE-2026-40686In 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).
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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
- 3.7 LOW (v3.1, CNA)CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:L/I:N/A:N
- Weakness (CWE)
- CWE-125
- Known exploited
- Not in CISA's KEV catalog
- EPSS (exploitation in the next 30 days)
- Not loaded for this CVE
- Assigned by
- mitre
- NVD analysis
- Analyzed
- Record last updated
- May 1, 2026
- First seen by InfoSec Signals
- Oct 9, 2026
Affected products
References
- https://www.openwall.com/lists/oss-security/2026/04/30/21mailing-list, third-party-advisory
- https://exim.org/static/doc/security/cve-2026-04.1/CVE2026-40686.assessmentvendor-advisory
- https://code.exim.org/exim/exim/commit/f2570bde16fb4d4a1242ff363a4c4eecf6372efcpatch
- https://exim.org/static/doc/security/CVE-2026-40686.txtbroken-link
The CVE record on cve.org NVD's entry
The CVE record is authoritative. Products marked “from the name” were identified from the CNA's free-text names, not a CPE, and are matched less certainly. This product uses the NVD API but is not endorsed or certified by the NVD.