VulnerabilityAnalyzed
CVE-2026-40686
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).
MEDIUM 5.3EPSS 0.25%
Does this matter?
Lower severity and a low EPSS score (0.25%). Track it; it rarely justifies an emergency change on its own.
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
- 5.3 MEDIUMCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:N/A:N
- EPSS
- 0.25% probability · 16th percentile
- CISA KEV
- Not listed
- Weakness
- CWE-125
- Affected
- exim/exim
- Source
- cve@mitre.org
References
- https://code.exim.org/exim/exim/commit/f2570bde16fb4d4a1242ff363a4c4eecf6372efcPatch
- https://exim.org/static/doc/security/CVE-2026-40686.txtBroken Link
- https://exim.org/static/doc/security/cve-2026-04.1/CVE2026-40686.assessmentVendor Advisory
- https://www.openwall.com/lists/oss-security/2026/04/30/21Mailing List, Third Party Advisory
Source: NVD record, EPSS from FIRST.org, KEV from CISA. Refreshed daily.