Authentication Bypass by Spoofing in Rsync - CVE-2026-53791
Published: August 13, 2026
Vulnerability identifier: #VU142288
CSH Severity: High
CVSS v4: 9.3 [CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:H/VI:H/VA:N/SC:N/SI:N/SA:N]
CVE-ID: CVE-2026-53791
CWE-ID: CWE-290
Exploitation vector: Remote access
Exploit availability:
No public exploit available
Vulnerability details
The vulnerability allows a remote attacker to bypass host-based access control and spoof the daemon\'s source address.
The vulnerability exists due to authentication bypass by spoofing in PROXY-protocol mode when handling a direct client connection with a supplied PROXY header. A remote attacker can send a forged PROXY header to bypass host-based access control and spoof the daemon\'s source address.
The issue occurs when proxy protocol = true is enabled and the client connects directly rather than through a trusted proxy.
Affected software
Rsync
How to mitigate CVE-2026-53791
Install security update from vendor's website.
Rsync - update to 3.5.0