← Vulnerability feed

Vulnerability record · CVE-2026-40685 · published 30 April 2026

CVE-2026-40685: Exim out-of-bounds write vulnerability

Exim · Exim

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.

9.8 CVSS 3.1 Critical EPSS 0.58% · top 54.7% CWE-684 · CWE-684CWE-787 · Out-of-bounds write
9.8CVSS 3.1 base score
0.58%EPSS exploitation probability, 30 days
NoNot in CISA KEV
1Affected product versions listed by NVD
4References
17 Jun 2026Last modified by NVD

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.

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

Affected products

1 vulnerable configurations from NVD's CPE data, grouped by vendor and product.

References

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

Track CVE-2026-40685 inside VULONE

Watch it alongside the ransomware crews, C2 infrastructure and forum chatter that reference it, query it through the API and pull it into your SIEM over TAXII.

Start free Open in platform

Related vulnerabilities

Same products first, then exploited flaws of the same weakness class.

9.8CVE-2019-16928Exim heap buffer overflow in string_vformat via long EHLO commandExim 4.92 through 4.92.2 contains a heap-based buffer overflow in string_vformat in string.c triggered by a long EHLO command, allowing remote code e…KEVEPSS 42%analysed9.8CVE-2019-10149Exim MTA improper recipient validation leads to remote command executionExim versions 4.87 through 4.91 fail to properly validate recipient addresses in the deliver_message() function in /src/deliver.c, allowing command i…KEVEPSS 100%analysed9.8CVE-2018-6789Exim SMTP base64d buffer overflow allows remote code executionExim before 4.90.1 contains a buffer overflow in the base64d function of its SMTP listener. A handcrafted message can trigger the overflow, and the f…KEVEPSS 82%analysed9.8CVE-2010-4344Exim SMTP heap buffer overflow enables remote code executionExim before 4.70 has a heap-based buffer overflow in string_vformat in string.c. A remote SMTP session that sends two MAIL commands plus a large mess…KEVEPSS 72%analysed7.8CVE-2010-4345Exim local privilege escalation via alternate config file command injectionExim 4.72 and earlier lets the exim user account specify an alternate configuration file whose directives can contain arbitrary commands, as shown wi…KEVEPSS 18%analysed9.8CVE-2026-45185Exim use after free vulnerabilityExim before 4.99.3, in certain GnuTLS configurations, has a remotely reachable use-after-free in the BDAT body parsing path. It is triggered when a c…EPSS 0.94%9.8CVE-2025-67896Exim heap-based buffer overflow vulnerabilityExim before 4.99.1, with certain non-default rate-limit configurations, allows a remote heap-based buffer overflow because database records are cast …EPSS 0.47%9.8CVE-2025-26794Exim SQL injection via SQLite hints and ETRN serializationExim 4.98 before 4.98.1 allows remote SQL injection when SQLite hints and ETRN serialization are used. The flaw is a CWE-89 SQL injection reachable o…EPSS 77%analysed

Source: NIST National Vulnerability Database (record CVE-2026-40685), CISA KEV, FIRST EPSS (scores of 2026-09-28). This page is refreshed as NVD updates the record.