Track vulnerabilities like this one.
Sign up free to get alerted when software you use is affected.
8.3
CVE-2026-52735: Zebra node may accept invalid Zcash blocks
CVE-2026-52735 · published 2 months ago
Summary
Zebra versions before 4.5.0 could count certain transaction signatures incorrectly, letting blocks pass Zebra validation that the official Zcash software rejects. This mismatch could cause a split in the network if Zebra miners include those blocks. Upgrade Zebra to version 4.5.0 or later to fix the counting error.
What to do
- Update conradoplg zebra-script to version 7.0.0.
- Update conradoplg zebrad to version 4.5.0.
- Update zebra-script to version 7.0.0.
- Update zebrad to version 4.5.0.
Affected software
| Ecosystem | Vendor | Product | Affected versions |
|---|---|---|---|
| crates.io | conradoplg | zebra-script |
< 7.0.0 Fix: upgrade to 7.0.0
|
| crates.io | conradoplg | zebrad |
< 4.5.0 Fix: upgrade to 4.5.0
|
| rust | conradoplg | zebrad |
<= 4.4.1 Fix: upgrade to 4.5.0
|
| rust | conradoplg | zebra-script |
<= 6.0.1 Fix: upgrade to 7.0.0
|
| – | zcashfoundation | zebra | < 4.5.0 |
| rust | – | zebra-script |
<= 6.0.1 Fix: upgrade to 7.0.0
|
| rust | – | zebrad |
<= 4.4.1 Fix: upgrade to 4.5.0
|
Original advisory text
ZEBRA: Consensus divergence via P2SH sigop undercount in pure-Rust disabled-opcode parser
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.
References
- https://github.com/ZcashFoundation/zebra Product
- https://github.com/AlfredoG87/zcash_script/blob/v0.4.4/src/script/iter.rs#L104-L...
- https://github.com/advisories/GHSA-gf9r-m956-97qx
- https://github.com/ZcashFoundation/zebra/releases/tag/v4.5.0 URL
- https://github.com/ZcashFoundation/zebra/security/advisories/GHSA-gf9r-m956-97qx Vendor Advisory
- https://github.com/ZcashFoundation/zebra/commit/1440b43ca7df59aca948090d45117557... Patch
- https://github.com/ZcashFoundation/zebra/blob/d4cd662c716382f6397d2a730148025a1c...
- https://github.com/ZcashFoundation/zebra/blob/d4cd662c716382f6397d2a730148025a1c...
- https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/52xxx/CVE-2026-52735... Vendor Advisory
- https://nvd.nist.gov/vuln/detail/CVE-2026-52735 Vendor Advisory
Internet-facing
14 days
Internal
60 days
- Not known to be exploited
- Can be exploited automatically
- Gives an attacker partial control
Severity
8.3
High
Type
CWE-684Incorrect Provision of Specified Functionality
Timeline
Published18 Aug 2026
Updated30 Oct 2026
First seen2 Jul 2026
Sources
GHSA-gf9r-m956-97qx · GHSA
CVE-2026-52735 · NVD
GHSA-gf9r-m956-97qx · OSV
CVE-2026-52735 · MITRE
CVE-2026-52735 · OSV
Track software like this
Free during beta