CVE-2026-40685
criticalIn 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…
Vendor / product: Exim — exim
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.
CVSS
9.8
9.8 (CVSS v3.1)
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H Severity source: NVD CVSS v3.1 (nvd@nist.gov)
Timeline (UTC)
Published: 2026-04-30 22:16
Modified: 2026-11-11 21:10
NVD status: Analyzed
Last synced 5 hours ago
Verified against the source API 2026-11-11 21:11 UTC
Exploitation
Not listed in CISA KEV (as of last catalog sync)
Absence from KEV does not mean a CVE is not exploited. Exploitation status: unknown (no authoritative evidence in our sources).
Affected products
exim / exim <4.99.2
Weakness classification (CWE)
Source: NVD / CISA. “NVD-CWE-Other” and “NVD-CWE-noinfo” mean NVD could not assign a specific weakness.
Mitigation & advisories
Patch / mitigation: https://code.exim.org/exim/exim/commit/9fdc057e71b87c87a0d3d2288b2810a0efaaba57
References
- https://code.exim.org/exim/exim/commit/9fdc057e71b87c87a0d3d2288b2810a0efaaba57 cve@mitre.org
- https://exim.org/static/doc/security/CVE-2026-40685.txt cve@mitre.org
- https://exim.org/static/doc/security/cve-2026-04.1/CVE2026-40685.assessment cve@mitre.org
- https://www.openwall.com/lists/oss-security/2026/04/30/21 cve@mitre.org
Data sources
NVD CVE API 2.0 — fetched 2026-11-11 21:11 UTC · record ↗