CVE-2026-55556

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.

CVSS

No CVSS.

References

Link	Resource
https://github.com/rsyslog/rsyslog/commit/acde2ba25ea33816694b787859f4a727a247b6d6
https://github.com/rsyslog/rsyslog/pull/6722
https://github.com/rsyslog/rsyslog/releases/tag/v8.2604.0
https://github.com/rsyslog/rsyslog/security/advisories/GHSA-947w-69ph-mc2r
http://www.openwall.com/lists/oss-security/2026/06/23/4
https://github.com/rsyslog/rsyslog/security/advisories/GHSA-947w-69ph-mc2r

Configurations

No configuration.

History

22 Sep 2026, 16:17

Type	Values Removed	Values Added
References	~~() https://github.com/rsyslog/rsyslog/security/advisories/GHSA-947w-69ph-mc2r -~~	() https://github.com/rsyslog/rsyslog/security/advisories/GHSA-947w-69ph-mc2r -

18 Sep 2026, 18:17

Type	Values Removed	Values Added
References		() http://www.openwall.com/lists/oss-security/2026/06/23/4 -

18 Sep 2026, 17:16

Type	Values Removed	Values Added
New CVE

Information

Published : 2026-09-18 17:16

Updated : 2026-09-24 21:22

NVD link : CVE-2026-55556

Mitre link : CVE-2026-55556

CVE.ORG link : CVE-2026-55556

JSON object : View

Products Affected

No product.

CWE

CWE-122

Heap-based Buffer Overflow

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