Assessment
Why it matters
EPSS is 0.3%; technical severity is CVSS 5.3.
Exim 4.88 before 4.99.4, in some proxy configurations, mishandles certain short payloads, leading to disclosure of uninitialized stack memory values to a client.
Who should care
- Teams operating Exim
- Vulnerability and exposure management teams
- Security operations teams monitoring exploitation activity
Response plan
What I would do
- Confirm whether Exim is present in the environment.
- Identify affected versions and establish whether vulnerable services are exposed or reachable.
- Debian Security advisory Msg00004
- Review relevant security telemetry for evidence of attempted or successful exploitation.
- Document the remediation decision and track it to verified completion.
Treatment intelligence
Remediation intelligence
Vendor sources are listed before government and third-party guidance. Confirm product applicability and change prerequisites before deployment.
Verification noteAutomated link verification has not completed for this guidance yet.
Mitigation
Technical details
- CVSS vector
- CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:N/A:N
- CWE
- CWE-839
- Affected versions
- Exim Exim (Start Including 4.88, End Excluding 4.99.4)
- Fixed versions
- Exim Exim (Fixed from 4.99.4)
- Published
- 30 May 2026
- Attack vector
- Network
- Privileges required
- None
- User interaction
- None
Signal timeline
- CVE published
- Latest EPSS score: 0.3%
- Signal calculated at 9