CVE-2026-66746: tomaka rouille HTTP Request/Response Splitting

Vulnerability summary

CVE-2026-66746 is a medium (CVSS 5.4) HTTP Request/Response Splitting vulnerability in tomaka rouille. EPSS estimates a 0.34% chance of exploitation in the next 30 days, higher than 26.1% of scored vulnerabilities. 1 public exploit is recorded.

Timeline

1. 28-07-2026
   PublishedVulnerability first disclosed.
2. 29-07-2026
   Last modifiedVulnerability information updated.

Description

Rouille 0.4.0 through 3.6.2 contains an HTTP response splitting vulnerability that allows remote attackers to inject arbitrary response headers by embedding carriage return (0x0D) or line feed (0x0A) bytes into attacker-controlled input. Attackers can exploit percent-decoded query parameters reflected into response headers or inject bare LF characters into Cookie header values that are interpolated directly into Set-Cookie response headers, enabling cache poisoning, session fixation, and security header override attacks such as bypassing CSP or CORS policies.

• CWE-113Improper Neutralization of CRLF Sequences in HTTP Headers ('HTTP Request/Response Splitting')The product receives data from an HTTP agent/component (e.g., web server, proxy, browser, etc.), but it does not neutralize or incorrectly neutralizes CR and LF characters before the data is included in outgoing HTTP headers.