Use After Free in Exim
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.
Vulnerability class: Use-After-Free
Published · last modified .
CVSS v3 metric
CVSS v3 base score 9.8 (Critical). Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H.
EPSS exploit prediction
EPSS: 0.009 (60.4th percentile), scored .
Very low probability of exploitation in the next 30 days; routine patching cadence is appropriate. 60th percentile — 60.4% of CVEs in the catalogue have a lower EPSS than this one. How to read EPSS.
EPSS over last 30 days · oldest: 0.012 · newest: 0.009 · change: -0.003
Affected products
- Exim — versions 4.97
Weakness classification (CWE)
Public proof-of-concept exploits
References
- 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 (Issue Tracking)
- www.openwall.com/lists/oss-security/2026/05/12/4 (Mailing List, Third Party Advisory)
- xbow.com/blog/dead-letter-cve-2026-45185-xbow-found-rce-exim (Third Party Advisory)
- af854a3a-2127-422b-91ae-364da2661108 (Mailing List, Third Party Advisory)
Frequently asked questions
- What is CVE-2026-45185?
- CVE-2026-45185 is a critical-severity vulnerability in Exim, classified under Use After Free. CVSS score: 9.8/10. Published 2026-05-12.
- How severe is CVE-2026-45185?
- Critical severity. CVSS v3 base score is 9.8 out of 10.
- Is CVE-2026-45185 known to be exploited?
- 4 public proof-of-concept repositories are indexed. Not currently listed in the CISA KEV catalog.