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 products
exim: exim
References8
- code.exim.org/exim/wiki/wiki/EximSecurity Vendor Advisory
- exim.org Product
- exim.org/static/doc/security/CVE-2026-45185.txt Broken Link
- exim.org/static/doc/security/EXIM-Security-2026-05-01.1/ Release Notes
- news.ycombinator.com/item?id=48111748 Issue Tracking
- www.openwall.com/lists/oss-security/2026/05/12/4 Mailing ListThird Party Advisory
- xbow.com/blog/dead-letter-cve-2026-45185-xbow-found-rce-exim Third Party Advisory
- www.openwall.com/lists/oss-security/2026/05/12/25 Mailing ListThird Party Advisory
Metrics
- CVSS 3.1
-
9.8
CRITICAL
Score source: CNA
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H - EPSS — exploit probability
- 1% percentile: 70 · as of 14 November 2026
- CWE
- CWE-416
Could this be exploited in your environment?
A patch closes the known hole. A penetration test shows what an attacker can still reach — with proof.