CVE-2026-40684
HIGH
7.5
CVSS Score
Published: April 30, 2026 at 12:00 AM UTC
Updated: June 17, 2026 at 10:45 AM UTC
1 product affected across 1 vendorExim
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Severity
HIGH7.5
Exploit prediction
EPSS 0.4%
SSVC
No known exploit
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.
Remediation
No guide yetNo remediation guidance has been written for this CVE yet. What the record does show:
References (6)
Source: cverecord
https://exim.org/static/doc/security/CVE-2025-40684.txtMailing ListThird Party Advisory
Source: cverecord
https://www.openwall.com/lists/oss-security/2026/04/30/21Vendor Advisory
Source: cverecord
https://exim.org/static/doc/security/cve-2026-04.1/CVE2026-40684.assessmentPatch
Source: cverecord
https://code.exim.org/exim/exim/commit/628bbaca7672748d941a12e7cd5f0122a4e18c81Source: af854a3a-2127-422b-91ae-364da2661108
http://www.openwall.com/lists/oss-security/2026/05/01/11SSVC — Action Prioritization
SSVCNo known exploitNot automatablePartial impact
SSVC signals action urgency (what to patch first), separate from CVSS which measures severity.
CVSS
- Attack Vector
- NETWORK
- Complexity
- LOW
- Privileges
- NONE
- User Interaction
- NONE
- Scope
- UNCHANGED
- Confidentiality
- NONE
- Integrity
- NONE
- Availability
- HIGH
Vector?
Quick Info
StatusMODIFIED
CWE
CWE-684
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