CVE-2026-45185: Exim use-after-free in BDAT body parsing with GnuTLS

CVE-2026-45185 · Severity: critical · CVSS 9.8 · Published 2026-05-12

Exim is a widely used mail server responsible for routing and delivering email across the internet. A critical security flaw has been identified that allows an unauthenticated attacker to take complete control of the server remotely. This could lead to the theft of sensitive emails, disruption of communication services, or a total compromise of the underlying system.

Technologies: Exim. Vendors: Exim.

Quick answers

Is CVE-2026-45185 exploited in the wild?
No. Junglewise Threat Intelligence has no report of CVE-2026-45185 being exploited in the wild.
How severe is CVE-2026-45185?
Critical severity, with a CVSS score of 9.8, published 12 May 2026.
Which products and versions are affected?
Exim 4.97 through 4.99.x before 4.99.3, 4.97 up to (excluding) 4.99.3.
Is there a fix for CVE-2026-45185?
A patch was published on 2026-05-12: Fixed in Exim version 4.99.3 Junglewise finds every place you run it, drafts the upgrade and applies it once you approve.
How is CVE-2026-45185 attacked?
It is attacked over the network, in a hosted service.
Am I affected by CVE-2026-45185?
Check whether you run Exim at an affected version. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.

Technical details

A use-after-free (UAF) vulnerability exists in Exim's BDAT body parsing path when configured with GnuTLS. The flaw is triggered during a CHUNKING transfer if a client sends a TLS 'close_notify' mid-body, followed by a final cleartext byte on the same TCP connection. This sequence causes a mismatch in object lifecycles between Exim and the GnuTLS library, leading to heap corruption. An unauthenticated remote attacker can exploit this to achieve arbitrary code execution with the privileges of the Exim process. The issue is fixed in Exim version 4.99.3.

Affected products

  • Exim Exim 4.97 up to (excluding) 4.99.3

Timeline

  • 2025-05-01: disclosed: Vulnerability submitted to Exim security team
  • 2026-05-12: advisory: Public release and coordinated disclosure
  • 2026-05-12: patched: Fixed in Exim version 4.99.3

References

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