CVE-2026-53791

rsync daemon before 3.5.0 contains an IP address spoofing vulnerability that allows unauthenticated remote attackers to bypass IP-based access controls by sending a crafted PROXY protocol header with a forged source address. Attackers who can connect directly to the rsync daemon can inject a spoofed source IP in the PROXY protocol header to circumvent hosts allow/deny rules, gaining unauthorized access that would otherwise be blocked based on their real source address.

CVSS vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N

• https://github.com/RsyncProject/rsync/releases/tag/v3.5.0
• https://github.com/RsyncProject/rsync/security/advisories/GHSA-h2q9-5fr8-w635
• https://www.vulncheck.com/advisories/rsync-daemon-ip-spoofing-via-proxy-protocol-header