CVE-2026-52735
NVD analysis in progress
ZEBRA is a Zcash node written entirely in Rust. Prior to 4.5.0, Zebra can accept a block that zcashd rejects because the P2SH signature-operation counter undercounts redeem scripts containing a disabled opcode followed by signature opcodes. In zebra-script/src/lib.rs, p2sh_input_sigop_count used the pure-Rust script::Code::sig_op_count path, whose try_fold parser stops at disabled opcodes such as OP_CODESEPARATOR and returns only the partial count accumulated before the error. The zcashd reference implementation continues static signature-operation counting through disabled opcodes, so an attacker can broadcast P2SH spends that Zebra counts below MAX_BLOCK_SIGOPS while zcashd counts above the 20,000-operation limit. If a Zebra miner includes those transactions, Zebra validators accept the block while zcashd validators reject it, creating a consensus chain split that affects network integrity and availability without requiring the attacker to produce a block. This issue is fixed in version 4.5.0.
What this means
- Exposure
- Exploitable remotely over the network, without authentication and with no action from the victim.
- Impact
- An attacker can modify or destroy data. The impact spreads beyond the vulnerable component into other parts of the system.
- Likelihood
- Its EPSS score stays low: nothing points to imminent exploitation, which is no reason to leave it unpatched.
What to doPatch without waiting for the next scheduled cycle. Start with the instances exposed to the internet.
Read automatically from the CVSS vector, the weakness type (CWE) and the EPSS score. The technical description above remains the one published by NIST.