PT-2026-36196 · Exim+2 · Exim+2

Bernard Quatermass · Published 2026-04-29 · Updated 2026-06-03 · CVE-2026-40685

Positive Technologies (AI Summary)

CVSS v3.1

9.8

Critical

Base vector

AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H

Name of the Vulnerable Software and Affected Versions Exim versions prior to 4.99.2

Description An out-of-bounds heap write can occur when JSON lookup is enabled. This happens when a JSON operator encounters malformed JSON in an untrusted header due to an incorrect implementation of backslash skipping.

Recommendations Update to version 4.99.2 or later. As a temporary workaround, disable the JSON lookup feature to minimize the risk of exploitation.

Fix

Memory Corruption

Weakness Enumeration

CWE-684

CWE-787

Related Identifiers

CVE-2026-40685

USN-8228-1

USN-8382-1

Affected Products

Exim

Linuxmint

Ubuntu

References · 28

• https://ubuntu.com/security/CVE-2026-40686 · Vendor Advisory
• https://osv.dev/vulnerability/UBUNTU-CVE-2026-40685 · Vendor Advisory
• https://osv.dev/vulnerability/DEBIAN-CVE-2026-40685 · Vendor Advisory
• https://ubuntu.com/security/CVE-2026-48840 · Vendor Advisory
• https://security-tracker.debian.org/tracker/CVE-2026-40685 · Vendor Advisory
• https://ubuntu.com/security/CVE-2023-51766 · Vendor Advisory
• https://code.exim.org/exim/exim/commit/9fdc057e71b87c87a0d3d2288b2810a0efaaba57 · Patch
• https://osv.dev/vulnerability/USN-8228-1 · Vendor Advisory
• https://osv.dev/vulnerability/USN-8382-1 · Vendor Advisory
• https://ubuntu.com/security/CVE-2026-40687 · Vendor Advisory
• https://ubuntu.com/security/CVE-2026-40685 · Vendor Advisory
• https://nvd.nist.gov/vuln/detail/CVE-2026-40685 · Security Note
• https://ubuntu.com/security/CVE-2026-45185 · Vendor Advisory
• https://exim.org/static/doc/security/cve-2026-04.1/CVE2026-40685.assessment · Vendor Advisory
• https://ubuntu.com/security/notices/USN-8228-1 · Vendor Advisory