CVE-2026-40685: Exim

Critical severity, CVSS 9.8. EPSS: 0.6% chance of exploitation in the next 30 days.

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.

Affected products

• Exim Exim: before 4.99.2 (fixed in 4.99.2)

Published 2026-04-30. Last modified 2026-06-17.