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01 Record

CVE-2026-40684

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

MediumPUBLISHEDCNA: mitre
CNA base score5.9 CVSS v3.xCVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:H

02 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

03 Exploitation and scoring

Exploitation
Assessed, none found. CISA's assessment recorded neither public exploit code nor evidence of exploitation when it was made.
SSVC decision
  • ExploitationnoneCISA recorded no public exploit code and no evidence of exploitation.
  • AutomatablenoAt least one step from reconnaissance to exploitation cannot be reliably automated.
  • Technical ImpactpartialSuccessful exploitation gives limited control of the vulnerable component.
CISA publishes the decision points, not a final SSVC decision. The decision also depends on mission and well-being impact, which is a property of your deployment rather than of the vulnerability.
EPSS probability
0.36% probability of exploitation activity in the next 30 days.
EPSS percentile
Equal to or higher than the score of 29.7% of scored records. A rank, not a probability.
NVD base score
7.5 (CVSS v3.x), scored by the NVD independently of the CNA.
NVD CVSS vector
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
NVD analysis status
Modified. NVD last modified this record on 2026-06-17.
Red Hat severity
No Red Hat rating. Red Hat rates the CVEs that affect its products.

Exploit-prediction scores from FIRST. Independent scoring and analysis status from the NVD. Vendor severity from Red Hat. Exploitation assessment and catalog membership from CISA.

04 Metadata

Published
2026-04-30 00:00Z6 MO AGO
Last updated
2026-05-01 17:22Z6 MO AGO
Reserved
2026-04-14
Assigning CNA
mitre
Record state
PUBLISHED
Severity
Medium (CVSS 5.9)
CNA CVSS vector
CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:H
Weaknesses
  • CWE-684Incorrect Provision of Specified FunctionalityClass
Data version
5.2
Document digest
bbb0263e0d45ba713360467c44685cf52116b44ca0a100f52211f2c1c30e1d08

05 Affected products

VendorProductVersionsPlatforms
EximExim0 to < 4.99.2—

06 References

07 Fixed in

Debian 12

  • exim4
    Fixed in 4.96-15+deb12u9

Source: Debian Security Tracker, the Debian security team. Received through OSV.dev. Reformatted by exploit.cc.

Debian 13

  • exim4
    Fixed in 4.98.2-1+deb13u2

Source: Debian Security Tracker, the Debian security team. Received through OSV.dev. Reformatted by exploit.cc.

Debian 14

  • exim4
    Fixed in 4.99.2-1

Source: Debian Security Tracker, the Debian security team. Received through OSV.dev. Reformatted by exploit.cc.

A release or ecosystem missing from this list has no record here. It may be unaffected or not covered by the source. Source notices and licences.