Defuse

**Name of the Vulnerable Software and Affected Versions** ZEBRA versions prior to 4.4.0 **Description** The block validator undercounts transparent signature operations against the 20000-sigop block limit `MAX BLOCK SIGOPS`, which allows the software to accept blocks that zcashd rejects. This discrepancy can enable a miner to split the network, as Zebra nodes would follow a chain that zcashd nodes reject. The issue stems from two undercounting errors: first, the `Sigops` implementation skipped the coinbase input entirely, allowing up to approximately 98 sigops to be hidden in the coinbase `scriptSig`. Second, Zebra failed to accumulate P2SH sigops during block validation, only computing them during the mempool-acceptance path. Consequently, blocks where the aggregate redeem-script sigops exceed 20000 are incorrectly accepted. **Recommendations** Update to version 4.4.0.