Use-after-free in Exim - CVE-2026-94055
Published: September 29, 2026 / Updated: October 7, 2026
Vulnerability identifier: #VU152756
CSH Severity: Medium
CVSS v4: 6.9 [CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:L/SC:N/SI:N/SA:N]
CVE-ID: CVE-2026-94055
CWE-ID: CWE-416
Exploitation vector: Remote access
Exploit availability:
No public exploit available
Vulnerability details
The vulnerability allows a remote attacker to cause a denial of service.
The vulnerability exists due to a use-after-free in GnuTLS TLS-on-connect handling when accepting TLS-on-connect connections. A remote attacker can initiate a TLS-on-connect connection to cause a denial of service.
The installation must use GnuTLS 3.6.4 or later, accept TLS-on-connect connections, and enable the non-default tls_early_banner_hosts option.
Affected software
Exim
Fedora
Ubuntu
exim4 (Ubuntu package)
exim
Fedora
Ubuntu
exim4 (Ubuntu package)
exim
How to mitigate CVE-2026-94055
Install security update from vendor's website.
Exim - update to 4.100.1
exim4 (Ubuntu package) - update to 4.99.1-1ubuntu1.5
exim - addressed in versions 4.100.1-1.el8, 4.100.1-1.el9, 4.100.1-1.el10_4, 4.100.1-1.fc43
exim4 (Ubuntu package) - update to 4.99.1-1ubuntu1.5
exim - addressed in versions 4.100.1-1.el8, 4.100.1-1.el9, 4.100.1-1.el10_4, 4.100.1-1.fc43