CVE-2020-37268 Coq and Rocq Prover Print Assumptions Omits Unsafe Universe Checking Inlined Through Parameter Inline
Attackers can bypass audit checks in Coq by hiding unsafe universe operations behind inlined parameters, allowing proofs of false statements to appear valid.
- 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-2020-37268?
CVE-2020-37268 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
Print Assumptions does not report that a definition was produced while universe checking was disabled when that definition reaches the caller through Parameter Inline in a module type. Applying a functor inlines the body of the parameter, and the inlining drops the record that the term was built under Unset Universe Checking, so the resulting constant carries no trace of the unsafe operation. A module implementation can therefore prove False using a universe inconsistency, expose it through an inlined parameter, and have Print Assumptions report the dependent proof as closed under the global context. Because Print Assumptions is the in-process audit used to confirm that a development rests on no unexpected assumptions, a dependency built this way passes that audit while proving arbitrary propositions. The standalone checker coqchk does reject the resulting compiled file. The project records this in dev/doc/critical-bugs.md under non-fixed bugs and rates the risk as moderate when coqchk is not used.
Weakness: CWE-778
Which versions are affected by CVE-2020-37268?
How do I fix CVE-2020-37268?
No fix has been published for CVE-2020-37268 yet. Limit exposure of the affected software until one is available.
Is CVE-2020-37268 being exploited?
It is not confirmed as exploited in the wild, but public exploit code for CVE-2020-37268 exists.
Public exploit code: 1 proofs of concept on GitHub.
Sources
Also known as GHSA-5fm4-65fg-j439.