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CVE-2026-40685 Details

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.

Metrics

CVSS 3.x Severity and Vector Strings:

NIST: [email protected]CVSS-B:9.8 CRITICALVector:CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H

CNA: [email protected]CVSS-B:6.5 MEDIUMVector:CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:L/A:H

References to Advisories, Solutions, and Tools

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URL	Source(s)	Tag(s)
https://code.exim.org/exim/exim/commit/9fdc057e71b87c87a0d3d2288b2810a0efaaba57	[email protected]	Patch
https://exim.org/static/doc/security/cve-2026-04.1/CVE2026-40685.assessment	[email protected]	Vendor Advisory
https://exim.org/static/doc/security/CVE-2026-40685.txt	[email protected]	Broken Link
https://www.openwall.com/lists/oss-security/2026/04/30/21	[email protected]	Mailing ListThird Party Advisory

Weakness Enumeration

CWE-ID	CWE Name	Source
CWE-787	Out-of-bounds Write	[email protected]
CWE-684	Incorrect Provision of Specified Functionality	[email protected]

Affected Products

Product	Versions
exim exim	< 4.99.2
CPE cpe:2.3:a:exim:exim:::::::: Remediation No remediation found in references.

Change History

5 change records found show changes

Date	Action	Recorded By
Jun 17, 2026	CVE Modified	[email protected]
Jun 17, 2026	CVE Modified	CISA-ADP
May 1, 2026	Initial Analysis	[email protected]
May 1, 2026	CVE Modified	[email protected]
Apr 30, 2026	New CVE Received	[email protected]