Heap-based buffer overflow in rsyslog - CVE-2026-55556
Published: June 24, 2026
Vulnerability identifier: #VU135091
CSH Severity: Medium
CVSS v4.0: CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N/E:U/U:Green
CVE-ID: CVE-2026-55556
CWE-ID: CWE-122
Exploitation vector: Remote access
Exploit availability:
No public exploit available
Vendor: rsyslog.com
Affected software:
rsyslog
rsyslog
Detailed vulnerability description
The vulnerability allows a remote attacker to cause a denial of service.
The vulnerability exists due to a heap-based buffer overflow in parse_auth_header() in the imhttp module when processing a crafted HTTP Basic Authorization header. A remote attacker can send a single crafted HTTP request to cause a denial of service.
Only deployments where the optional imhttp module is installed, explicitly loaded, and configured with HTTP Basic Authentication for an endpoint are vulnerable.
How to mitigate CVE-2026-55556
Install security update from vendor's website.