Out-of-bounds write in Exim - CVE-2026-40687
Published: May 7, 2026
Vulnerability identifier: #VU130457
CSH Severity: Medium
CVSS v4.0: CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:L/VI:N/VA:H/SC:N/SI:N/SA:N/E:U/U:Green
CVE-ID: CVE-2026-40687
CWE-ID: CWE-787
Exploitation vector: Remote access
Exploit availability:
No public exploit available
Vendor: Exim
Affected software:
Exim
Exim
Detailed vulnerability description
The vulnerability allows a remote attacker to cause a denial of service.
The vulnerability exists due to out-of-bounds read/write in the SPA authentication driver when handling a hostile or compromised external SPA/NTLM connection. A remote attacker can provide crafted SPA/NTLM responses to cause a denial of service.
The issue is exposed in configurations that use the SPA authentication driver and may also leak heap data to the instance.
How to mitigate CVE-2026-40687
Install security update from vendor's website.