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.
Metrics
Affected Vendors & Products
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Advisories
| Source | ID | Title |
|---|---|---|
 Github GHSA |
GHSA-gf9r-m956-97qx | zebrad has consensus divergence via P2SH sigop undercount in pure-Rust disabled-opcode parser |
Fixes
Solution
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Workaround
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References
History
Tue, 18 Aug 2026 19:30:00 +0000
| Type | Values Removed | Values Added |
|---|---|---|
| Description | 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. | |
| Title | ZEBRA: Consensus divergence via P2SH sigop undercount in pure-Rust disabled-opcode parser | |
| Weaknesses | CWE-684 | |
| References |
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| Metrics |
cvssV4_0
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Projects
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MITRE
Status: PUBLISHED
Assigner: GitHub_M
Published:
Updated: 2026-08-18T19:48:45.150Z
Reserved: 2026-06-08T14:00:43.572Z
Link: CVE-2026-52735
Vulnrichment
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NVD
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Redhat
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OpenCVE Enrichment
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Weaknesses