Vulnerability · Published Jul 28, 2026 · Assigned by VulnCheck

CVE-2026-66754Rouille 0.1.6 - 3.6.2 Reachable Assertion DoS via remove_prefix percent-encoding

Medium 5.9

In plain English

A medium-severity security flaw in rouille from tomaka. Proof-of-concept exploit code is public. The chance it is exploited in the next 30 days is estimated at 0.6% (higher than 47% of all known vulnerabilities). Ready-made attack tooling exists: public proof-of-concept code.

Severity (CVSS 3.1)5.9Medium

Exploit odds (30 days)0.6%top 52.9% of all CVEs

Exploited in the wildNo reportsCISA SSVC: poc

Attack tooling1Public PoC

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.

Affected packages & fixed versions

Ecosystem	Package	Fixed in	Advisory
Debian:14	rust-rouille	no fix listed	DEBIAN-CVE-2026-66754

Affected products (as reported)

Vendor	Product	Versions
tomaka	rouille	0.1.6 – through 3.6.2

Weakness: CWE-617 · Vector: CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:H

References

Researcher Disclosure technical-description, exploit
https://www.vulncheck.com/advisories/rouille-reachable-assertion-dos-via-remove-prefix-percent-encoding third-party-advisory