CVE-2026-40685

Name: CVE-2026-40685
Creator: NVD / NIST
Published: 2026-04-30T22:16:25.633+00:00
License: https://creativecommons.org/publicdomain/zero/1.0/

CRITICALCVSS 9.8/10EPSS 0.32%

Last modified Jun 17, 2026

CVE-2026-40685 is a critical-severity vulnerability rated 9.8/10 on the CVSS scale. 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.. EPSS estimates a 0.32% chance of exploitation in the next 30 days.

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 3.1

9.8/10

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

EPSS Probability

0.32%

23.8th percentile

Probability of exploitation in the next 30 days. Learn more

Weakness Enumeration

Affected Software

Vendor	Product	Versions
Exim	Exim	< 4.99.2

References

https://code.exim.org/exim/exim/commit/9fdc057e71b87c87a0d3d2288b2810a0efaaba57Patch
https://exim.org/static/doc/security/CVE-2026-40685.txtBroken Link
https://exim.org/static/doc/security/cve-2026-04.1/CVE2026-40685.assessmentVendor Advisory
https://www.openwall.com/lists/oss-security/2026/04/30/21Mailing List, Third Party Advisory

Timeline

Published: Apr 30, 2026
Last Modified: Jun 17, 2026
Status: Analyzed

Frequently Asked Questions

What is CVE-2026-40685?

How severe is CVE-2026-40685?

CVE-2026-40685 has a CVSS score of 9.8/10 (CRITICAL severity). The EPSS model estimates a 0.32% probability of exploitation in the next 30 days.

How do I fix CVE-2026-40685?

Check the vendor references and advisories linked above for patched versions and mitigation guidance. You can also run a Strix scan to test if your systems are affected.

Are you affected by CVE-2026-40685?

Run a free Strix scan to check your systems for this vulnerability.

Scan your code now

Source: NVD / NIST