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.…
Exact source revision recorded 28 Oct 2026 07:15:36 UTC. It does not establish the source's current position. Latest evidence.
euvd · EUVD-2026-61166
PublishedZEBRA 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.
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datePublished: Aug 18, 2026, 7:23:10 PM
dateUpdated: Aug 18, 2026, 7:48:45 PM
- Source published
- Aug 18, 2026, 7:23:10 PM (timezone not stated)
- Source modified
- Aug 18, 2026, 7:48:45 PM (timezone not stated)
- Observed here
- 28 Oct 2026 07:15:36 UTC
- Source terms
- ENISA EUVD · source terms and attribution apply
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EUVD CVSS 4.0 · 9.3 CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:H/VA:N/SC:N/SI:H/SA:H