CVE-2026-66746 Rouille 0.4.0 - 3.6.2 HTTP Response Splitting via Header Injection
Remote attackers can inject headers in Rouille library, enabling cache poisoning and security policy bypasses via response splitting.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Over the internet
- Victim action needed
- A user has to click or open something
- Fix
- Available
What is CVE-2026-66746?
CVE-2026-66746 is a medium-severity vulnerability in tomaka rouille, published on 28 Jul 2026. An attacker can exploit it over the internet without logging in, and only if a user opens a file or follows a link.
Official 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.
Weakness: CWE-113
Which versions are affected by CVE-2026-66746?
How do I fix CVE-2026-66746?
Upgrade to a fixed version.
Is CVE-2026-66746 being exploited?
It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-66746 exists.
Public exploit code: 1 proofs of concept on GitHub.
Sources
Also known as DEBIAN-CVE-2026-66746, GHSA-998j-f97v-vpgr.