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CVE-2026-40684

Published: Apr 30, 2026Updated: May 1, 2026 Sources: CVE List NVDCWE-684
NVD MITRE
5.9CVSSMEDIUM
EPSS Score
0.4%
Top 72.2%
CISA KEV
Not in KEV
Exploits
No Known Exploits
Remediation
Patch Available

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.

CVSS Vector Breakdown

AV:NAC:HPR:NUI:NS:UC:NI:NA:H
Exploitability
AV:NAttack Vector
Network
AC:HAttack Complexity
High
PR:NPrivileges Required
None
UI:NUser Interaction
None
Scope
S:UScope
Unchanged
Impact
C:NConfidentiality
None
I:NIntegrity
None
A:HAvailability
High
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Weaknesses

CWE-684

Affected Products

EximExim
On-prem
Communications / email-server-client
eximexim
On-prem
Communications / email-server-client
eximoss-projectCommunications

Exploitability

Official Patch Available

References

https://www.openwall.com/lists/oss-security/2026/04/30/21
openwall.com
https://exim.org/static/doc/security/cve-2026-04.1/CVE2026-40684.assessment
exim.org
https://code.exim.org/exim/exim/commit/628bbaca7672748d941a12e7cd5f0122a4e18c81
code.exim.org
and 2 more references View all →

Timeline

Published
Apr 30, 2026
Last Updated
May 1, 2026

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