Vulnerability · Published May 12, 2026 · Assigned by mitre
CVE-2026-45185
Critical 9.8
In plain English
A critical-severity use-after-free in Exim from Exim. There are no confirmed reports of exploitation so far. The chance it is exploited in the next 30 days is estimated at 1.3% (higher than 70% of all known vulnerabilities). Ready-made attack tooling exists: public proof-of-concept code. Fixed versions are available - upgrade the affected package.
Official description
Exim before 4.99.3, in certain GnuTLS configurations, has a remotely reachable use-after-free in the BDAT body parsing path. It is triggered when a client sends a TLS close_notify mid-body during a CHUNKING transfer, followed by a final cleartext byte on the same TCP connection. This can lead to heap corruption. An unauthenticated network attacker exploiting this vulnerability could execute arbitrary code.
Affected packages & fixed versions
| Ecosystem | Package | Fixed in | Advisory |
|---|---|---|---|
| Debian:12 | exim4 | 4.96-15+deb12u9 | DEBIAN-CVE-2026-45185 |
| Debian:13 | exim4 | 4.98.2-1+deb13u2 | DEBIAN-CVE-2026-45185 |
| Debian:14 | exim4 | 4.99.2-2 | DEBIAN-CVE-2026-45185 |
| Ubuntu:22.04:LTS | exim4 | 4.95-4ubuntu2.8 | UBUNTU-CVE-2026-45185 |
| Ubuntu:24.04:LTS | exim4 | 4.97-4ubuntu4.5 | UBUNTU-CVE-2026-45185 |
| Ubuntu:25.10 | exim4 | 4.98.2-1ubuntu2.2 | UBUNTU-CVE-2026-45185 |
| Ubuntu:26.04:LTS | exim4 | 4.99.1-1ubuntu1.2 | UBUNTU-CVE-2026-45185 |
Affected products (as reported)
Weakness: CWE-416 · Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
References
- https://exim.org
- https://code.exim.org/exim/wiki/wiki/EximSecurity
- https://exim.org/static/doc/security/CVE-2026-45185.txt
- https://xbow.com/blog/dead-letter-cve-2026-45185-xbow-found-rce-exim
- https://news.ycombinator.com/item?id=48111748
- https://www.openwall.com/lists/oss-security/2026/05/12/4
- https://exim.org/static/doc/security/EXIM-Security-2026-05-01.1/
- http://www.openwall.com/lists/oss-security/2026/05/12/25