Denial of service in Zebra via unscored script verification failures
Key facts
- Attack vector
- Network
- Privileges required
- None
- User interaction
- None
- Attack complexity
- Low
- Attack requirements
- None
- Impact type
- —
- Confidentiality · integrity · availability
- None · None · High
- Fix status
- Fixed
Attack profile from CVSS 4.0 · CNA. Fix status from CNA.
Summary
ZcashFoundation Zebra from 2.3.0 before 7.0.0 and from 1.0.0-beta.46 before 18.0.0 fails to score peers that send invalid transparent scripts as misbehavior, so those peers evade penalties (CWE-755). An unauthenticated remote peer can flood the mempool or serve forged v5 block bodies with altered scriptSig bytes, exhausting CPU and repeatedly stalling block sync.
Written with Claude Haiku 5.5 from the sources below · 2026-11-08
Description from the CNA
Zebra from 2.3.0 before 7.0.0 contains a denial of service vulnerability that allows unauthenticated peers to evade misbehavior scoring by sending transactions or blocks with invalid transparent scripts. Attackers can flood mempool with script-failing transactions or serve forged v5 block bodies with altered scriptSig bytes to exhaust CPU and repeatedly stall block sync.
Why it matters now
SSVC decision points
Not available: CISA has not published SSVC decision points for this record.
Affected products
| Vendor | Product | Affected versions | Fixed in | Status | Source |
|---|---|---|---|---|---|
| ZcashFoundation | zebra | 2.3.0 to before 7.0.0 | 7.0.0 | Patch available | CNA |
| ZcashFoundation | zebra | 1.0.0-beta.46 to before 18.0.0 | 18.0.0 | Patch available | CNA |
- zebra VendorZcashFoundation Affected 2.3.0 to before 7.0.0 Fixed in 7.0.0 Patch available CNA
- zebra VendorZcashFoundation Affected 1.0.0-beta.46 to before 18.0.0 Fixed in 18.0.0 Patch available CNA
Remediation
Upgrade ZcashFoundation Zebra to version 7.0.0 for the 2.3.0 line or to version 18.0.0 for the 1.0.0-beta.46 line. The sources list no advisory identifiers for this fix.
Written with Claude Haiku 5.5 from the sources below · 2026-11-08
- Fix · CNA zebra (ZcashFoundation) Fixed in 7.0.0
- Fix · CNA zebra (ZcashFoundation) Fixed in 18.0.0
Fixed in the same release
Records fixed by the same vendor advisory or release, as the CNA lists them.
- Release ·
ZcashFoundation zebra 7.0.0
7 records Highest priority Priority MEDIUM 7 MEDIUM
Other records, highest priority first
- TI-2026-86702 Incomplete cleanup in Zebra lets peers stall initial syncPriority MEDIUM 53
- TI-2026-86701 Quadratic signature hashing in Zcash Zebra enables denial of servicePriority MEDIUM 53
- TI-2026-86700 Improper cleanup stalls Zebra checkpoint sync via a malicious peerPriority MEDIUM 53
Timeline
- 2026-11-08 Threatist record created from CVE-2026-123555
- 2026-11-08 Alias added: GHSA-cwcw-qfgm-5r6m
References
Patch 1
More ZcashFoundation vulnerabilities
- 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
Sources
- CVE-2026-123555 · CVE Program
- CVE-2026-123555 · NVD
- GHSA-cwcw-qfgm-5r6m · GitHub Advisory Database · CC BY 4.0
This product uses the NVD API but is not endorsed or certified by the NVD. Sources and licences