CVE-2026-40686
medium
CVSS v3
5.3
CVSS v4 NEW
—
VIR risk
5.3
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.
Predictions
Exploit likelihood
63%
Patch ETA
—
Heuristic predictions, AS-IS, for prioritization only.
Mitigations
No mitigations published for this CVE yet.
The vendor-content worker queues fetches as references arrive (check back in a few minutes). Or — if you've already worked around this in production — publish your fix to the community-verified tier.
✚ Propose a mitigation on Community → Mitigations published via the community go through AI scoring + 2 human reviewers + 7-day silent objection window before landing here withsource_tier=community-verified.
OS impact
| OS | Version | Status | Fixed in |
|---|---|---|---|
| debian | bookworm | fixed | 4.96-15+deb12u9 |
| debian | bullseye | affected | |
| debian | forky | fixed | 4.99.2-1 |
| debian | sid | fixed | 4.99.2-1 |
| debian | trixie | fixed | 4.98.2-1+deb13u2 |
Application impact
| Vendor | Product | Versions | Fixed |
|---|---|---|---|
| exim | exim | {"endExcluding":"4.99.2"} | 4.99.2 |
References
- https://code.exim.org/exim/exim/commit/f2570bde16fb4d4a1242ff363a4c4eecf6372efc
- https://exim.org/static/doc/security/CVE-2026-40686.txt
- https://exim.org/static/doc/security/cve-2026-04.1/CVE2026-40686.assessment
- https://www.openwall.com/lists/oss-security/2026/04/30/21
- https://security-tracker.debian.org/tracker/CVE-2026-40686
CWEs
CWE-125
Community-verified mitigations for this CVE will appear above when contributors publish them.
Verify integrity in audit chain (admin only). AS-IS.