Proof integrity bypass via unchecked opaque declarations
Published Aug 24, 2026 · Updated Aug 24, 2026
Improper input validation in the Lean 4 kernel before 4.32.2 allows local users to admit false propositions through crafted metaprograms. environment::add_opaque omits the closure check on an opaque body, while a stale inference-cache entry supplies a type before local-context membership is tested. Exploitation requires a crafted metaprogram to run in the affected Lean process; an accepted false constant invalidates every proposition derived from it.
Summary
What happened
Improper input validation in the Lean 4 kernel before 4.32.2 allows local users to admit false propositions through crafted metaprograms. environment::add_opaque omits the closure check on an opaque body, while a stale inference-cache entry supplies a type before local-context membership is tested. Exploitation requires a crafted metaprogram to run in the affected Lean process; an accepted false constant invalidates every proposition derived from it.
The record
- CVE
- CVE-2026-72711
- Published
- Aug 24, 2026
- Updated
- Aug 24, 2026
- Vendor
- Lean FRO
- Product
- Lean 4
- Classifications
- CWE-20
- Attack vector
- local
- Privileges
- unauthenticated
Timeline
How it unfolded
- Aug 24, 2026CVE publishedPublication date reported by the CVE source.
- Aug 24, 2026Record updatedLatest update available in the CVE record.
Exploitability
Present is not the same as exploitable
Compare your product and version with the public record. A matching version still requires validation against your environment.
Is a vulnerable build present?
Compare these published version ranges with your installed build and any vendor patches.
- Affected versionversion=0 <4.32.2
What conditions does exploitation require?
What is affected?
Attacks
What attackers are doing with it
Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.
Weakness, pattern, technique
Public exploit references
- Lean 4 kernel inference-cache poisoning proof of conceptfunctional · demonstrated
Labels summarize the accepted research assessment. They do not indicate a test against your environment.
Technologies
Your stack
See the directory against your own environment.
Your stack
Check the software in your environment
Book a demo to see how Hinoki identifies affected software and validates exploitability in your environment.
Book a demo