CVE-2026-55556

Rsyslog: Heap buffer overflow in imhttp plugin Basic Authentication handling

Published: Sep 18, 2026Updated: Sep 22, 2026 Sources: CVE List NVDCWE-122

N/ACVSS

NVD MITRE

Description

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.

No summary for this CVE yet.

Weaknesses

CWE-122

Affected Products

rsyslog

oss-projectaka rsyslogd, librelp

rsyslogOn-prem

Enterprise Software / itsm-monitoring

Exploitability

No known exploits, KEV entries, or remediation guidance available for this vulnerability yet.

Attack Graph

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MITRE ATT&CK

1 technique

Privilege Escalation

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References

https://github.com/rsyslog/rsyslog/commit/acde2ba25ea33816694b787859f4a727a247b6d6

github.com

https://github.com/rsyslog/rsyslog/pull/6722

github.com

https://github.com/rsyslog/rsyslog/releases/tag/v8.2604.0

github.com

and 2 more references View all →

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