CVE-2026-66754 Rouille 0.1.6 - 3.6.2 Reachable Assertion DoS via remove_prefix percent-encoding
Remote attackers can crash the server by sending crafted percent-encoded URLs that trigger a reachable assertion failure in the Rouille library.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Over the internet
- Victim action needed
- Not needed
- Fix
- Available
What is CVE-2026-66754?
CVE-2026-66754 is a high-severity denial of service vulnerability in tomaka rouille, published on 28 Jul 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.
Official description
Rouille 0.1.6 through 3.6.2 contains a reachable assertion vulnerability in the Request::remove_prefix function that allows remote unauthenticated attackers to crash the server by sending a crafted percent-encoded URL. Attackers can send a request whose decoded path matches a configured prefix while the raw percent-encoded path does not, causing the assert! to fail and triggering either a 500 error or full process termination depending on the panic configuration.
Weakness: CWE-617
Which versions are affected by CVE-2026-66754?
How do I fix CVE-2026-66754?
Upgrade to a fixed version.
Upgrade, then put limits on request size, rate and nesting depth so one client cannot exhaust the service. More about Denial of service.
Is CVE-2026-66754 being exploited?
It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-66754 exists.
Public exploit code: 1 proofs of concept on GitHub.
Sources
Also known as DEBIAN-CVE-2026-66754, GHSA-mrg5-7f6c-r28q.