CVE-2026-40687 Memory corruption in Exim
An out-of-bounds write in Exim's SPA authentication driver can crash the service or leak heap memory when processing adversarial input.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Over the internet
- Victim action needed
- Not needed
- Fix
- Available
What is CVE-2026-40687?
CVE-2026-40687 is a medium-severity memory corruption vulnerability in Exim Exim, published on 30 Apr 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.
Official description
In Exim before 4.99.2, when the SPA authentication driver is used with an adversarial SPA resource, there can be an out-of-bounds write that crashes the connection instance, or erroneous data processing that divulges data from uninitialized heap memory.
Weakness: CWE-909
Which versions are affected by CVE-2026-40687?
It affects 1 product.
Products include Exim Exim.
How do I fix CVE-2026-40687?
Upgrade to a fixed version.
Upgrade to the fixed version. Memory-safe languages, compiler hardening and fuzzing prevent most new cases. More about Memory corruption.
Is CVE-2026-40687 being exploited?
There is no known exploitation of CVE-2026-40687 in the wild and no public exploit code.
Other vulnerabilities in Exim Exim
Sources
Also known as CLSA-2026-1778024392, CLSA-2026-1778024757, DEBIAN-CVE-2026-40687, GHSA-x8x4-4g6x-cx4h, ROOT-OS-DEBIAN-11-CVE-2026-40687, UBUNTU-CVE-2026-40687.