CVE-2026-40684 Details
Description
In Exim before 4.99.2, on systems using musl libc (not glibc), an attacker can crash the connection instance when malformed DNS data is present in PTR records. This is caused by a dn_expand oddity in octal printing.
A denial-of-service vulnerability has been identified in Exim versions prior to 4.99.2, specifically on systems using musl libc instead of glibc. The issue arises when malformed DNS data in PTR records is processed, leading to a crash of the Exim connection instance. This behavior is linked to an oddity in how octal printing is handled by musl libc.
Users can upgrade to Exim version 4.99.2, which is available as a tarball from the Exim FTP site or directly from Git. Instructions for verifying the release signature are also provided.
Metrics
CVSS 4.0 Severity and Vector Strings:
No CVSS 4.0 data is available for this CVE.
CVSS 3.x Severity and Vector Strings:
No data available for CVSS Version 2.0 on this CVE.
CISA-ADP
Assessed May 1, 2026References to Advisories, Solutions, and Tools
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Weakness Enumeration
| CWE-ID | CWE Name | Source |
|---|---|---|
| CWE-684 | Incorrect Provision of Specified Functionality | [email protected] |
Affected Products
| Product | Versions |
|---|---|
| exim exim | < 4.99.2 |
CPE
Remediation
| |
Change History
6 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 | CVE Modified | CVE |
| May 1, 2026 | Initial Analysis | [email protected] |
| May 1, 2026 | CVE Modified | [email protected] |
| Apr 30, 2026 | New CVE Received | [email protected] |