Paper/Archive/CVE-2026-40685

CVE-2026-40685

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…

EPSS 0.3%CVSS 9.8

critical.is priorityof 100

CVSS 9.8 (NVD)9.8 / 10 × 3029.4 Not in CISA KEV+300.0 EPSS percentile 25.1.251 × 205.0 No public exploit+100.0 SSVC exploitation: none+100.0

Description · from the CVE record

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

ProductAffectedFixed inSource

Exim< 4.99.24.99.2CNA

Scores by source

NVD9.8CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H

mitre (CNA)6.5CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:L/A:H

CISA ADPSSVCExploitation: none · Automatable: no · Technical impact: partial

References

refopenwall.com/lists/oss-security/2026/04/30/21 refexim.org/static/doc/security/cve-2026-04.1/CVE2026-40685.assessment refcode.exim.org/exim/exim/commit/9fdc057e71b87c87a0d3d2288b2810a0efaaba57 refexim.org/static/doc/security/CVE-2026-40685.txt