CVE-2026-40685: In Exim before 4.99.2, when JSON lookup is enabled, an out-of-bounds heap write can occur when a JSON operator…
CVE-2026-40685 · Severity: medium · CVSS 6.5 · Published 2026-04-30
In Exim before 4.99.2, when JSON lookup is enabled, an out-of-bounds heap write can occur when a JSON operator encounters malformed JSON in an untrusted header, because of an incorrect implementation of \ skipping.
No. Junglewise Threat Intelligence has no report of CVE-2026-40685 being exploited in the wild.
How severe is CVE-2026-40685?
Medium severity, with a CVSS score of 6.5, published 30 April 2026.
Which products and versions are affected?
Exim. The advisory does not name versions.
Is there a fix for CVE-2026-40685?
No fixed version is recorded yet. Check the vendor's advisory in the references below. If you run it, Junglewise drafts a mitigation that fits your setup and applies it once you approve, with senior security engineers behind it.
Am I affected by CVE-2026-40685?
Check whether you run Exim. 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.