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Vulnerabilities

Vulnerability · 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.

Published Apr 30, 2026 · catalog updated Jun 17, 2026 · In Exim before 4.99.2,

Check if you run it

No confirmed exploitation is on record for CVE-2026-40684. EPSS is 0.61%. Act only if a listed version of In Exim before 4.99.2, is installed.

Gaps on this record

  • The stored product name is a package slug. The name on this page is taken from the title (In Exim before 4.99.2,).
  • No version range is stored. A customer cannot check an installed version against this record.
  • No vendor fix or required action is stored. Compare the linked advisory before you change production.
Severity
High7.5
Known exploitation
Not in CISA/VulnCheck KEV
EPSS
0.61%
Remediation
Advisory link
Affected products
cpe exim/exim

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.

Are you affected?

Enter the version you run. The result uses only the ranges stored on this record.

The check returns affected, not affected, or incomplete. It does not guess a version that is missing from the record.

  • cpe exim/eximversion unspecified

How to fix CVE-2026-40684

What to do

Three questions, each answered from this record only. Confirm the vendor advisory before you patch.

Should you patch?

No confirmed exploitation is on record for CVE-2026-40684. EPSS is 0.61%. Act only if a listed version of In Exim before 4.99.2, is installed.

Which versions are affected?

Affected version ranges are not on this record. Compare the installed version with the linked vendor advisory before you change production.

What should an analyst verify?

CWE-684. EPSS 0.61%. There is no CISA KEV listing. No Exploit-DB or Metasploit reference is linked. Use the source links for the original advisory.

Code

The project this record applies to. Exploit listings stay in References.

No public source repository is identified for this product.

Timeline

Detection, updates, and resolution for this record.

  1. Apr 30, 2026 · NIST NVD

    Detected

    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.

  2. Jun 17, 2026 · NIST NVD

    Updated

    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.

Sources

  • CVE.orgVulnerability recordCVE-2026-40684

    Official CVE identifier

    cve.org
  • FIRST EPSSExploitation probabilityCVE-2026-40684

    30-day exploitation probability 0.6%

    first.org
  • NIST NVDVulnerability recordCVE-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 octal printing.

    nvd.nist.gov

References

Freshness

Last verified in this catalog Oct 18, 2026. Significant claims (KEV, EPSS, CVSS, affected ranges) come from the source rows above — open the original publisher for the authoritative advisory.