CVE-2026-55556
Severity not reportedRsyslog is a rocket-fast system for log processing.
Rsyslog is a rocket-fast system for log processing. From 8.2110.0 until 8.2604.0, the optional imhttp module's parse_auth_header function in contrib/imhttp/imhttp.c allocates a zero-byte heap buffer with calloc(0, len) when an HTTP Basic Authorization value exceeds its fixed work buffer, then passes that pointer to apr_base64_decode. An unauthenticated remote attacker can send an oversized encoded credential to an imhttp endpoint configured for Basic Authentication, causing decoded data to overwrite adjacent heap memory before credential validation. Deployments that do not install, load, and use imhttp with Basic Authentication are not affected. The demonstrated impact is a process crash that interrupts log collection, and code execution has not been demonstrated. This issue is fixed in version 8.2604.0.
Affected products
Not reported by the source (unknown — not "none").
Weakness classification (CWE)
Source: NVD / CISA. “NVD-CWE-Other” and “NVD-CWE-noinfo” mean NVD could not assign a specific weakness.
Mitigation & advisories
No vendor advisory or patch reference tagged by NVD. Check the references below.
References
- https://github.com/rsyslog/rsyslog/commit/acde2ba25ea33816694b787859f4a727a247b6d6 security-advisories@github.com
- https://github.com/rsyslog/rsyslog/pull/6722 security-advisories@github.com
- https://github.com/rsyslog/rsyslog/releases/tag/v8.2604.0 security-advisories@github.com
- https://github.com/rsyslog/rsyslog/security/advisories/GHSA-947w-69ph-mc2r security-advisories@github.com
- http://www.openwall.com/lists/oss-security/2026/06/23/4 af854a3a-2127-422b-91ae-364da2661108
- https://github.com/rsyslog/rsyslog/security/advisories/GHSA-947w-69ph-mc2r 134c704f-9b21-4f2e-91b3-4a467353bcc0