CVE-2026-45185
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.
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A critical vulnerability in Exim (before 4.99.3) allows unauthenticated remote code execution. The bug is triggered via specific TLS and CHUNKING sequences during email body parsing. All Linux server administrators using Exim should update to the latest version immediately.
Severity
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:HCWE-416EPSS
Technical 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.
References
- https://code.exim.org/exim/wiki/wiki/EximSecurity
- https://exim.org
- https://exim.org/static/doc/security/CVE-2026-45185.txt
- https://exim.org/static/doc/security/EXIM-Security-2026-05-01.1/
- https://news.ycombinator.com/item?id=48111748
- https://www.openwall.com/lists/oss-security/2026/05/12/4
- https://xbow.com/blog/dead-letter-cve-2026-45185-xbow-found-rce-exim
- http://www.openwall.com/lists/oss-security/2026/05/12/25