Rouille 0.3.3 through 3.6.2 contains an HTTP request smuggling vulnerability that allows remote attackers to bypass access controls by injecting bare line feed characters (0x0A) into client-supplied request header values that are copied verbatim to upstream connections without validation. Attackers can craft a header value containing a complete additional HTTP request that is interpreted as a separate request by backends such as Go net/http and Python http.server, causing the backend to process a smuggled request with attacker-chosen method, path, and headers that bypasses the rouille handler's access control logic.
https://www.vulncheck.com/advisories/rouille-http-request-smuggling-via-proxy-header-injection
https://github.com/theopaid/HTTP-Request-Smuggling-Enables-Front-End-Access-Control-Bypass-rouille-
Published: 2026-07-28
Updated: 2026-07-28
Base Score: 6.1
Vector: CVSS2#AV:N/AC:H/Au:N/C:N/I:C/A:P
Severity: Medium
Base Score: 7.5
Vector: CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:C/C:N/I:H/A:L
Severity: High
Base Score: 6.9
Vector: CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:N/VI:L/VA:N/SC:H/SI:L/SA:N
Severity: Medium
EPSS: 0.00415