CVE-2026-72714: Rocq Prover through 9.2.0 Universe Checking State Desynchronised After Module Close
Rocq Prover does not restore the universe graph's copy of the universe checking flag when a module that locally disabled the check is closed. Local Unset Universe Checking inside a module is expected to last only until the module ends, and the global flag is restored, but the universe graph keeps its own copy which is left disabled. The two views then disagree: Test Universe Checking reports the check as enabled while the kernel continues to accept universe-inconsistent terms. With the constraint between two universes no longer enforced, Hurkens' paradox applies and yields a proof of False, from which any proposition follows. The proof uses no axioms, plugins or unsafe features once the module has closed, and Print Assumptions reports it as closed under the global context, so neither the assumption audit nor the flag query reflects the actual kernel state. No fix is available.
Affected Software
Event History
Frequently Asked Questions
What must an attacker or untrusted proof contributor do to exploit this issue?
They must locally disable universe checking inside a module and then close that module. After closure, the global flag appears restored, but the kernel's universe graph continues accepting universe-inconsistent terms, enabling a proof of False through Hurkens' paradox.
Can normal checks reveal that a development has been affected?
Not reliably. Test Universe Checking reports that checking is enabled, and Print Assumptions reports the resulting proof as closed under the global context, even though the kernel state remains desynchronized.
Does exploiting this require axioms, plugins, or unsafe features?
No. Once the module has closed, the described proof uses no axioms, plugins, or unsafe features.
What mitigation is available if patching is not possible?
No fix is available. The provided information does not identify a reliable detection or mitigation method beyond avoiding the described local disabling of universe checking within modules.