Vulnerability · Published Aug 24, 2026 · Assigned by VulnCheck
CVE-2026-72705Rocq Prover before 9.2.0 Guard Checker Accepts Fixpoint Passed as a Higher-Order Argument
Medium 6.3
In plain English
A medium-severity security flaw in rocq from rocq-prover. Proof-of-concept exploit code is public. The chance it is exploited in the next 30 days is estimated at 0.2% (higher than 7% of all known vulnerabilities). Ready-made attack tooling exists: public proof-of-concept code.
Official description
The guard checker in Rocq Prover does not follow recursive calls made through a fixpoint's own arguments. A fixpoint may pass itself as a higher-order argument to a second fixpoint, which then applies it to a value that is not a subterm of the structural argument. Passing the recursive function to a plain definition is rejected because the checker unfolds the definition and observes the call, but passing it to a fixpoint is accepted because higher-order recursive calls through fixpoint arguments are not tracked. This admits a type that is definitionally equal to its own negation, so self-application produces False in purely definitional code, without tactics, axioms, plugins or unsafe flags, and Print Assumptions reports the result as closed under the global context. Fixed in Rocq 9.2.0.
Affected products (as reported)
| Vendor | Product | Versions |
|---|---|---|
| rocq-prover | rocq | 0 – before 9.2.0 |
Weakness: CWE-670 · Vector: CVSS:3.1/AV:L/AC:L/PR:N/UI:R/S:C/C:N/I:H/A:N
References
- https://github.com/rocq-prover/rocq product
- https://github.com/rocq-prover/rocq/issues/21683 issue-tracking
- https://github.com/rocq-prover/rocq/pull/21684 issue-tracking, patch
- https://github.com/endrazine/rocq-cve-poc-21683 exploit
- VulnCheck Advisory: Rocq Prover before 9.2.0 Guard Checker Accepts Fixpoint Passed as a Higher-Order Argument third-party-advisory
- http://www.openwall.com/lists/oss-security/2026/10/26/6