High 8.2Published Sep 18, 2026

CVE-2026-55556Rsyslog: Heap buffer overflow in imhttp plugin Basic Authentication handling

Updated under an hour ago (2026-10-19 08:23 UTC)

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No exploitation reported and no EPSS estimate yet.

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Exploited in the last 30 days

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: 8.2 HIGH (v4.0, CNA)CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N
Weakness (CWE): CWE-122
Known exploited: Not in CISA's KEV catalog
EPSS (exploitation in the next 30 days): Not loaded for this CVE
Assigned by: GitHub_M
NVD analysis: Awaiting Analysis
Record last updated: Sep 22, 2026
First seen by InfoSec Signals: Oct 9, 2026

Affected products

Affected products

rsyslog rsyslog rsyslog:rsyslog (from the name)	from 8.2110.0, < 8.2604.0	CNA record

References

https://github.com/rsyslog/rsyslog/security/advisories/GHSA-947w-69ph-mc2rx-refsource-confirm
https://github.com/rsyslog/rsyslog/pull/6722x-refsource-misc
https://github.com/rsyslog/rsyslog/commit/acde2ba25ea33816694b787859f4a727a247b6d6x-refsource-misc
https://github.com/rsyslog/rsyslog/releases/tag/v8.2604.0x-refsource-misc
http://www.openwall.com/lists/oss-security/2026/06/23/4

The CVE record on cve.org NVD's entry

The CVE record is authoritative. Products marked “from the name” were identified from the CNA's free-text names, not a CPE, and are matched less certainly. This product uses the NVD API but is not endorsed or certified by the NVD.