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CVE-2026-40685

39
FAUCET Score

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 published: Apr 30, 2026Last modified: May 1, 2026

Impacted Technologies

VendorProductVersion(s)CPE
>= 0, < 4.99.2CPE match
cpe:2.3:a:exim:exim:*:*:*:*:*:*:*:*
< 4.99.2CPE matchmatch criteria
cpe:2.3:a:exim:exim:*:*:*:*:*:*:*:*

CVSS Data

CVSS version used by this source: 3.1

6.5MEDIUM

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

Attack Vector
NETWORK
Attack Complexity
HIGH
Privileges Required
NONE
User Interaction
NONE
Scope
UNCHANGED
Confidentiality Impact
NONE
Integrity Impact
LOW
Availability Impact
HIGH
Exploitability Score
2.2
Impact Score
4.2
CvssVersion
3.1

Exploit Intelligence

EPSS Score
0.32%
Probability of exploitation in next 30 days
EPSS Percentile
24.5%
Percentile rank of EPSS score among Peer Group
As of 2026-07-26
Model: v2026.06.15
This CVE's current EPSS score of 0.0032 is in the 4th percentile among its peer group of 36,835 CVEs.

Social Chatter

The average CVE in this peer group has 0.0 Twitter, 0.1 Reddit, 0.3 Bluesky, 0.3 Mastodon, and 2.4 GitHub mentions.

Media Mentions

No media coverage found for this CVE.

The average CVE in this peer group has 0.3 InfoSec Media, 0.0 Vendor Blog, and 0.0 Security Researcher mentions.

Remediation

Patch Available

Vendor Patches (4)

ubuntupatch availablevia ubuntu_usn
Product: exim4 (jammy)Fixed in: 4.95-4ubuntu2.7
ubuntupatch availablevia ubuntu_usn
Product: exim4 (noble)Fixed in: 4.97-4ubuntu4.4
ubuntupatch availablevia ubuntu_usn
Product: exim4 (questing)Fixed in: 4.98.2-1ubuntu2.1
ubuntupatch availablevia ubuntu_usn
Product: exim4 (resolute)Fixed in: 4.99.1-1ubuntu1.1

Vendor Advisories (1)

ubuntuUSN-8228-1

Exim vulnerabilities

May 4, 2026

References

code.exim.org / exim/exim/commit/9fdc057e71b87c87a0d3d2288b2810a0efaaba57
Patch
exim.org / static/doc/security/cve-2026-04.1/CVE2026-40685.assessment
Vendor Advisory
exim.org / static/doc/security/CVE-2026-40685.txt
Broken Link
openwall.com / lists/oss-security/2026/04/30/21
Mailing ListThird Party Advisory