Description
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
References4
- exim.org/static/doc/security/cve-2026-04.1/CVE2026-40685.assess… Vendor Advisory
- code.exim.org/exim/exim/commit/9fdc057e71b87c87a0d3d2288b2810a0… Patch
- exim.org/static/doc/security/CVE-2026-40685.txt Broken Link
- www.openwall.com/lists/oss-security/2026/04/30/21 Mailing ListThird Party Advisory
Metrics
- CVSS 3.1
-
9.8
CRITICAL
Score source: NVD
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H - EPSS — exploit probability
- 0% percentile: 25 · as of 13 November 2026
- CWE
- CWE-684CWE-787
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