Formal-Verification - CraftedSignal Threat Feed

Rocq Prover: Soundness vulnerability in guard checker (CVE-2026-72705)

hello@craftedsignal.io — Mon, 26 Oct 2026 04:24:18 +0000

The Rocq (formerly Coq) kernel contains a soundness vulnerability in its guard checker, identified as CVE-2026-72705. The flaw occurs because the guard checker fails to correctly track recursive calls made through a fixpoint's own arguments. This allows for the construction of proofs that appear valid but conclude false propositions, such as 0 = 1, without the use of axioms, tactics, plugins, or unsafe flags. The system reports these malformed proofs as closed under the global context.

Impact

The vulnerability compromises the integrity of formally verified proofs generated by the Rocq Prover. If an attacker produces a false proof in a system relying on Rocq for verification, the security or logic properties guaranteed by that proof are invalidated.

Recommendation

Identify all projects or systems utilizing the Rocq Prover to generate formal proofs.
Monitor official Rocq development channels for the release of a patched version.
Review critical proofs that were generated using affected versions of the Rocq kernel to verify they do not rely on the identified guard checker flaw.

Lean 4: Kernel soundness vulnerability via nested inductive projections (CVE-2026-72844)

hello@craftedsignal.io — Mon, 26 Oct 2026 02:22:56 +0000

A soundness vulnerability in the Lean 4 kernel (CVE-2026-72844) enables the construction of checked proofs of 'False' (e.g., 0 = 1). The flaw stems from two primary issues: the kernel fails to verify that the structure named in a projection expression matches the type of the value being projected, and the environment::add_inductive function in src/kernel/inductive.cpp fails to perform necessary type-checking for nested definitions. This compromise undermines the foundational logical guarantees of the theorem prover. No further update has been provided regarding fixed versions or mitigation timelines beyond the initial disclosure.

Impact

This vulnerability allows for the creation of arbitrary proofs of logically false propositions within the Lean 4 environment. It does not require the use of explicit axioms, the sorry keyword, unsafeCast operations, or the modification of .olean files, allowing the exploit to bypass standard verification checks.

Recommendation

Inventory environments utilizing Lean 4 for formal verification or critical logical proofs.
Monitor the official Lean 4 repository and the oss-security mailing list for the release of security patches or official mitigation guidance.
Review critical proof developments that depend on the integrity of the Lean 4 kernel; consider re-verifying proofs using patched versions once updates are available.

Rocq: Soundness vulnerability in module system (CVE-2026-72714)

hello@craftedsignal.io — Mon, 26 Oct 2026 02:22:26 +0000

A soundness flaw in the Rocq kernel, identified as CVE-2026-72714, allows the construction of proofs of False without the use of axioms, plugins, or unsafe flags. The issue arises from a desynchronization in the module system, where the environment fails to correctly restore the "Universe Checking" flag state after closing a module that had disabled this check locally. Consequently, Print Assumptions incorrectly reports the resulting proofs as closed under the global context. This vulnerability undermines the logical consistency of formal proofs within the affected environment.

Impact

The vulnerability allows users to generate cryptographically or logically invalid proofs that the system accepts as valid, including the derivation of 0 = 1. This could be exploited to bypass security or verification properties in formal proofs relying on Rocq.

Recommendation

Identify all projects using the Rocq kernel that rely on formal proof verification for security-critical properties.
Audit existing proof scripts for the use of "Local Unset Universe Checking" commands.
Review documentation from the Rocq Project for patch availability or guidance on disabling module-local universe checking until a fix is applied.