---
id: CVE-2026-52735
title: ZEBRA is a Zcash node written entirely in Rust
summary: >-
  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 opcod…
severity: critical
cwe:
  - CWE-684
vendor: zebra-script
product: zebra-script
affected:
  - zebra-script <= 6.0.1
  - zebrad <= 4.4.1
patched:
  - zebra-script 7.0.0
  - zebrad 4.5.0
published: '2026-08-18'
updated: '2026-09-09'
sourceUpdated: '2026-09-09T21:13:25.910'
source: NVD
sourceUrl: 'https://nvd.nist.gov/vuln/detail/CVE-2026-52735'
references:
  - url: >-
      https://github.com/ZcashFoundation/zebra/commit/1440b43ca7df59aca948090d45117557b217a6cd
    label: security-advisories@github.com
  - url: 'https://github.com/ZcashFoundation/zebra/releases/tag/v4.5.0'
    label: security-advisories@github.com
  - url: >-
      https://github.com/ZcashFoundation/zebra/security/advisories/GHSA-gf9r-m956-97qx
    label: security-advisories@github.com
  - url: >-
      https://github.com/AlfredoG87/zcash_script/blob/v0.4.4/src/script/iter.rs#L104-L115
  - url: >-
      https://github.com/ZcashFoundation/zebra/blob/d4cd662c716382f6397d2a730148025a1ca79fec/zebra-consensus/src/block.rs#L140
  - url: >-
      https://github.com/ZcashFoundation/zebra/blob/d4cd662c716382f6397d2a730148025a1ca79fec/zebra-script/src/lib.rs#L383-L400
  - url: 'https://github.com/advisories/GHSA-gf9r-m956-97qx'
tags:
  - nvd
  - ghsa
  - rust
epss: 0.00507
epssPercentile: 0.40704
ecosystem: rust
ingestedAt: '2026-07-02T20:42:45.868Z'
---

## Overview

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.

## Remediation

Refer to the linked advisories for vendor-supplied fixes and affected version ranges.

## Package advisory (CVE-2026-52735)

Affected packages:

- `zebra-script <= 6.0.1`
- `zebrad <= 4.4.1`

Patched in:

- `zebra-script 7.0.0`
- `zebrad 4.5.0`

Source: https://github.com/advisories/GHSA-gf9r-m956-97qx