Read the docs
TI-2026-37853 Aliases CVE-2026-52735GHSA-gf9r-m956-97qx

ZEBRA: Consensus divergence via P2SH sigop undercount in pure-Rust disabled-opcode parser

Priority MEDIUM 47CWE-684Published · Updated

Key facts

Attack vector
Network
Privileges required
None
User interaction
None
Attack complexity
Low
Attack requirements
None
Impact type
—
Confidentiality · integrity · availability
None · High · None
Fix status
Fixed

Attack profile from CVSS 4.0 · CNA. Fix status from CNA and GitHub.

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 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.

Why it matters now

Exploitation None reported CISA SSVC · not in CISA KEV
EPSS 0.00507 43rd percentileScored 2026-11-07
Fix Fixed zebra (ZcashFoundation): 4.5.0zebra-script (crates.io): 7.0.0+1 more product

SSVC decision points

CISA ADP · SSVC 2.0.3

Exploitation
None
Automatable
Yes
Technical impact
Partial

The decision (Track, Attend, Act) also depends on your mission and well-being impact; see CISA's SSVC guide.

Affected products

VendorProductAffected versionsFixed inStatusSource
ZcashFoundationzebrabefore 4.5.04.5.0Patch availableCNA
—zebra-script (crates.io)before 7.0.07.0.0Patch availableGHSA-gf9r-m956-97qx
—zebrad (crates.io)before 4.5.04.5.0Patch availableGHSA-gf9r-m956-97qx
  • zebra VendorZcashFoundation Affected before 4.5.0 Fixed in 4.5.0 Patch available CNA
  • zebra-script (crates.io) Vendor— Affected before 7.0.0 Fixed in 7.0.0 Patch available GHSA-gf9r-m956-97qx
  • zebrad (crates.io) Vendor— Affected before 4.5.0 Fixed in 4.5.0 Patch available GHSA-gf9r-m956-97qx

Remediation

  • Fix · CNA zebra (ZcashFoundation) Fixed in 4.5.0
  • Fix · GHSA-gf9r-m956-97qx zebra-script (crates.io) Fixed in 7.0.0 Advisory →
  • Fix · GHSA-gf9r-m956-97qx zebrad (crates.io) Fixed in 4.5.0 Advisory →

Timeline

  1. 2026-10-02 Threatist record created from CVE-2026-52735
  2. 2026-10-03 Alias added: GHSA-gf9r-m956-97qx

References

Other 7

  • TI-2026-66079 Zebra before 4.4.0 Consensus Split via SIGHASH_SINGLE Missing-Output Handling CVSS 4.0HIGH 8.3
  • TI-2026-37850 ZEBRA: Mempool transaction admission denial via single-peer inbound queue saturation CVSS 3.1MEDIUM 5.3
  • TI-2026-71182 Improper block validation in Zebra gossip lets peers drop new blocks CVSS 4.0MEDIUM 6.3
  • TI-2026-29537 Zebra: addr/addrv2 Deserialization Resource Exhaustion CVSS 4.0MEDIUM 6.3
  • TI-2026-86702 Incomplete cleanup in Zebra lets peers stall initial sync CVSS 4.0HIGH 8.7
  • TI-2026-86701 Quadratic signature hashing in Zcash Zebra enables denial of service CVSS 4.0HIGH 8.7
See all 51 →

Sources

This product uses the NVD API but is not endorsed or certified by the NVD. Sources and licences