CVE-2026-40685

Published Apr 30, 2026 CVSS 3.1 · 6.5 Medium EPSS < 1% KEV · Not listed
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.

Remediation

No solution or workaround provided in the CVE record

Tracking

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Advisories

Source ID Title
Debian DSA Debian DSA DSA-6265-1 exim4 security update
Ubuntu USN Ubuntu USN USN-8228-1 Exim vulnerabilities
Ubuntu USN Ubuntu USN USN-8382-1 Exim vulnerabilities
History
Type Values Removed Values Added
Title Exim Out-of-Bounds Heap Write in JSON Lookup
Type Values Removed Values Added
Weaknesses CWE-787
Type Values Removed Values Added
Metrics ssvc

{'options': {'Automatable': 'no', 'Exploitation': 'none', 'Technical Impact': 'partial'}, 'version': '2.0.3'}

Type Values Removed Values Added
Title Exim Out-of-Bounds Heap Write in JSON Lookup
Type Values Removed Values Added
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.
First Time appeared Exim
Exim exim
Weaknesses CWE-684
CPEs cpe:2.3:a:exim:exim:*:*:*:*:*:*:*:*
Vendors & Products Exim
Exim exim
References
Metrics cvssV3_1

{'score': 6.5, 'vector': 'CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:L/A:H'}

Weaknesses

Sources

Status
PUBLISHED
Assigner
mitre
Published
Updated
May 1, 2026, 2:26 PM
Reserved
Apr 14, 2026, 12:00 AM
Status
Analyzed
Published
Apr 30, 2026, 10:16 PM
Modified
Nov 11, 2026, 9:10 PM