Rsync versions before 3.4.3 contain an off-by-one out-of-bounds stack write vulnerability in the establish_proxy_connection() function in socket.c that allows network attackers to corrupt stack memory by sending a malformed HTTP proxy response. Attackers can exploit this by positioning themselves between the client and proxy or controlling the proxy server to send a response line of 1023 or more bytes without a newline terminator, causing a null byte to be written to an out-of-bounds stack address when the RSYNC_PROXY environment variable is set.
https://www.vulncheck.com/advisories/rsync-off-by-one-stack-write-via-http-proxy
https://github.com/RsyncProject/rsync/security/advisories/GHSA-8f85-j2cv-59m8
Published: 2026-05-20
Updated: 2026-05-20
Base Score: 2.6
Vector: CVSS2#AV:N/AC:H/Au:N/C:N/I:N/A:P
Severity: Low
Base Score: 3.1
Vector: CVSS:3.1/AV:N/AC:H/PR:N/UI:R/S:U/C:N/I:N/A:L
Severity: Low
Base Score: 2.1
Vector: CVSS:4.0/AV:N/AC:H/AT:N/PR:N/UI:A/VC:N/VI:N/VA:L/SC:N/SI:N/SA:N
Severity: Low