CVE-2026-72704

What it is

The guard checker in Rocq Prover does not recheck the recursive tree representation of an inductive type parameter after that parameter has been changed by transport. A fixpoint may apply a rewrite along an equality between types to its recursive argument, which the guard checker accepts because the inductive type is preserved, while the recursive tree recorded for the parameter is altered. A second fixpoint that calls the first inherits the altered recursive tree without verification, so a call that is not structurally decreasing is accepted as terminating. The resulting non-terminating definition proves that a natural number equals its own successor and therefore False, from which any proposition follows. The demonstration uses two axioms that follow from univalence and are consistent with the calculus of inductive constructions, so the contradiction comes from the guard check rather than from the assumptions. A fix is proposed but not merged.

At a glance

Exploitability

Can be exploited locally on the machine without logging in, but needs a user to act. High risk of data tampering.

Exploit odds

0.2% chance of exploitation in the next 30 days (EPSS).

Fix

A patch, advisory or fixed version is referenced. Upgrade or apply it.

Timeline

1. 2026-08-24 20:17 UTC PublishedDisclosed publicly on CVE.org and NVD
2. 2026-10-26 02:17 UTC Last updatedMost recent change to the record

Why it ranks here

• Exploited in the wild: no, CISA does not list it.
• Exploit odds: 0.2% in the next 30 days (EPSS).
• Severity: 6.8 MEDIUM (CVSS).
• Fix: a patch or advisory is linked.

Details

Published

2026-08-24 20:17 UTC

Last modified

2026-10-26 02:17 UTC

Exploit probability

0.2% · EPSS, next 30 days

Weakness

CWE-670

Record status

Deferred

Attack profile CVSS 4.0 · 6.8

Attack vector

Local

Complexity

Low

Attack requirements

None

Privileges needed

None

User interaction

Passive

Confidentiality

None

Integrity

High

Availability

None

Is it in your code?

Hand this to your coding agent. It searches your project for the affected products and checks versions. Nothing leaves your machine.

Read https://cve-list.com/agent/cve/CVE-2026-72704.md and follow it. Check whether this project is affected by CVE-2026-72704. Read only. Don't change anything and don't upload my code. Tell me yes, no or not sure, with the file as proof.

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