SNARK Verifier: Halo 2 aggregation mishandles point-at-infinity proof elements
Affects axiom-crypto snark-verifier before 0.2.5 when the Halo 2 loader is used in recursive aggregation circuits with an assigned proof point in an MSM term. Fixed in 0.2.5.
- Last modified
- Where the record stands: published, rejected by its publisher, or superseded by another id.What do these mean? →
- published
- Whether CISA lists it in its Known Exploited Vulnerabilities catalog: proof that attackers are using it.What do these mean? →
- Not listed in CISA KEV
- How many real-world setups can hit the bug, from the vendor's advisory and CISA data. It does not know your setup.What do these mean? →
- Unclear
- Fix
- Fixed in 0.2.5
- Whether working attack code is public (Exploit-DB, Metasploit, Nuclei or GitHub). Public code makes attacks easier.What do these mean? →
- None on Exploit-DB, Metasploit or GitHub
Summary
SNARK Verifier, a generic zero-knowledge proof (SNARK/zk-SNARK) verifier library used with the Halo 2 proving system, is affected. A malicious prover could submit a proof with a point encoded as the point at infinity, which may cause the aggregation step to compute an incorrect result, with the actual impact depending on the surrounding verification checks.
Summarized by anthropic/claude-haiku-5.5. Verify details against the original sources.
Read the original description
SNARK Verifier is a generic (S)NARK verifier. Prior to 0.2.5, the Halo 2 aggregation circuit can mishandle proof points encoded as the point at infinity. `EcPointLoader::multi_scalar_multiplication` places a `Value::Assigned(_)` base paired with `Value::Constant(ONE)` into its unscaled variable-base list and passes it directly to `sum_with_const`. The default shim delegates to halo2-lib `EccChip::sum`, whose incomplete affine addition assumes nonidentity input points. A prover-controlled proof point encoded as `(0, 0)` can therefore enter the final aggregation sum through the scalar-one shortcut and affect the MSM or accumulator computation. Practical exploitability depends on the surrounding aggregation and final-decider checks; the advisory does not establish universal acceptance of invalid proofs. This issue is fixed in version 0.2.5.
Timeline
- CVE published
- First seen by cve.now
Affected versions
- axiom-crypto snark-verifier
fixed in 0.2.5
References 4
GitHub · axiom-crypto/snark-verifier
GitHub · axiom-crypto/halo2-lib
Questions about CVE-2026-62337
What does this mean?
A proof element encoded as the point at infinity can enter the aggregation MSM or accumulator computation, where the code assumed non-identity inputs. Whether this matters depends on the surrounding aggregation and final-decider checks.Source: github.com
Am I affected, and how do I check?
Versions of axiom-crypto snark-verifier before 0.2.5 are affected when the Halo 2 loader is used in a recursive aggregation circuit and an assigned proof point appears in an MSM term with constant scalar one. Check the snark-verifier version in the project's Cargo.lock and whether the circuit uses the Halo 2 loader.Source: github.com
What should I do about it?
Upgrade snark-verifier to 0.2.5 or later.Source: github.com
Is it being exploited?
It is not in CISA's Known Exploited Vulnerabilities catalog, and CISA's SSVC assessment does not mark exploitation as active. That does not mean it has not been attacked: vendors and researchers can report attacks before CISA lists them. No public exploit code is tracked.Source: cve.now feed data