CVE-2026-40684
high
CVSS v3
7.5
CVSS v4 NEW
—
VIR risk
7.5
Description
In Exim before 4.99.2, on systems using musl libc (not glibc), an attacker can crash the connection instance when malformed DNS data is present in PTR records. This is caused by a dn_expand oddity in octal printing.
Predictions
Exploit likelihood
83%
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/628bbaca7672748d941a12e7cd5f0122a4e18c81
- https://exim.org/static/doc/security/CVE-2026-40684.txt
- https://exim.org/static/doc/security/cve-2026-04.1/CVE2026-40684.assessment
- https://www.openwall.com/lists/oss-security/2026/04/30/21
- http://www.openwall.com/lists/oss-security/2026/05/01/11
- https://security-tracker.debian.org/tracker/CVE-2026-40684
CWEs
CWE-684
Community-verified mitigations for this CVE will appear above when contributors publish them.
Verify integrity in audit chain (admin only). AS-IS.