{"id":"CVE-2026-48100","published":"2026-09-28T17:17:49.547","lastModified":"2026-09-28T18:17:22.120","description":"Payy is an Ethereum L2 zk-rollup for privacy preserving and regulatory compliant transactions. Prior to version 1.3.0, agg_agg forwards the compacted message stream from its inner proofs into a public messages: [Field; 1000] array, but it never checks that the unused tail of the outer array is zero. A registered prover can build a valid agg_final proof for an approved rollup block while inserting an extra burn message after the real messages. RollupV1.verifyRollup() then parses that public input as a normal burn and transfers USDC from the rollup contract to the attacker. This is a severe circuit soundness failure: the proof system accepts a public statement whose messages array is not fully derived from the verified inner proofs. On the current deployment, verifyRollup() is restricted to the existing allowlisted prover, so a fresh public caller cannot submit the invalid proof directly. That gate limits who can reach L1 today; it does not make the circuit statement sound. The issue becomes permissionless under the prover model described in the Payy whitepaper. Section 3.3.2 states: \"To join as a prover, the prover is required to submit a small stake\", and Section 3.3.1 states that if a prover fails to submit, \"other nodes can submit the block proof instead.\" In that model, an attacker only needs to become a registered prover and use public validator approval data for an already approved block. This issue has been patched in version 1.3.0.","cvssScore":null,"cvssSeverity":null,"cvssVector":null,"cwes":["CWE-349"],"vendors":[],"products":[],"references":[{"url":"https://github.com/polybase/payy/security/advisories/GHSA-fhxc-63vg-9gwr","tags":[]},{"url":"https://github.com/polybase/payy/security/advisories/GHSA-fhxc-63vg-9gwr","tags":[]}],"exploitRefs":[{"url":"https://github.com/polybase/payy/security/advisories/GHSA-fhxc-63vg-9gwr","tags":[]},{"url":"https://github.com/polybase/payy/security/advisories/GHSA-fhxc-63vg-9gwr","tags":[]}],"hasPoc":true,"ai":null}