CVE-2026-72703 Rocq Prover 8.20 before 9.2.0 Guard Checker Accepts Non-Terminating Fixpoint via Unchecked Cross-Calls
Attackers can exploit a guard checker flaw in Rocq Prover to prove False, enabling arbitrary code execution via logical inconsistency.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Local or same network only
- Victim action needed
- A user has to click or open something
- Fix
- None listed
What is CVE-2026-72703?
CVE-2026-72703 is a medium-severity vulnerability in rocq-prover rocq, published on 24 Aug 2026. It can only be exploited from the same machine or local network, and only if a user opens a file or follows a link.
Official description
The guard checker in Rocq Prover treats a parameter of a nested mutual fixpoint as uniform without examining calls between the different bodies of that fixpoint. find_uniform_parameters in kernel/inductive.ml inspects only self-recursive calls, so when no body calls itself the function concludes that every parameter is uniform. A parameter that grows through a cross-call from one body to another therefore keeps the subterm specification it inherited from the enclosing fixpoint, and a recursive call guarded by that specification is accepted although the argument is not structurally smaller. A non-terminating definition is admitted as structurally decreasing, which yields a term whose value equals its own successor and so a proof of False, from which any proposition follows. The proof requires no axioms, plugins or unsafe flags and Print Assumptions reports it as closed under the global context. Introduced in Coq 8.20 and fixed in Rocq 9.2.0.
Weakness: CWE-670
Which versions are affected by CVE-2026-72703?
How do I fix CVE-2026-72703?
No fix has been published for CVE-2026-72703 yet. Limit exposure of the affected software until one is available.
Is CVE-2026-72703 being exploited?
It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-72703 exists.
Public exploit code: 1 proofs of concept on GitHub.
Sources
Also known as GHSA-q4cf-fp8g-gjg9.