Heap-based Buffer Overflow Affecting rsyslog package, versions <8.2604.0-1


Severity

Recommended
low

Based on Debian security rating.

Threat Intelligence

EPSS
0.85% (57th percentile)

Do your applications use this vulnerable package?

In a few clicks we can analyze your entire application and see what components are vulnerable in your application, and suggest you quick fixes.

Test your applications
  • Snyk IDSNYK-DEBIANUNSTABLE-RSYSLOG-17431940
  • published24 Jun 2026
  • disclosed18 Sept 2026

Introduced: 24 Jun 2026

CVE-2026-55556  (opens in a new tab)
CWE-122  (opens in a new tab)

How to fix?

Upgrade Debian:unstable rsyslog to version 8.2604.0-1 or higher.

NVD Description

Note: Versions mentioned in the description apply only to the upstream rsyslog package and not the rsyslog package as distributed by Debian. See How to fix? for Debian:unstable relevant fixed versions and status.

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 Base Scores

version 3.1