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TI-2026-66066 Aliases CVE-2026-104423GHSA-4x5w-56x5-cmfr

Zebra before 6.2.1 Denial of Service via Uncapped V6 Shielded Proof Verification

Priority MEDIUM 44CWE-405Published · Updated

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

Zebra (zebrad) before 6.2.1 contains an asymmetric resource consumption vulnerability that allows unauthenticated peers to stall block verification by pushing V6 mempool transactions with invalid Halo2 proofs. Attackers can flood the shared unprioritized Halo2 verification queue with zero-fee transactions carrying zero-filled Orchard and Ironwood proofs, causing nodes to fall behind the chain tip.

Why it matters now

Exploitation None reported CISA SSVC · not in CISA KEV
EPSS 0.00343 28th percentileScored 2026-11-07
Fix Fixed zebra (ZcashFoundation): 6.2.1

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 6.2.16.2.1Patch availableCNA
  • zebra VendorZcashFoundation Affected before 6.2.1 Fixed in 6.2.1 Patch available CNA

Remediation

  • Fix · CNA zebra (ZcashFoundation) Fixed in 6.2.1

Fixed in the same release

Records fixed by the same vendor advisory or release, as the CNA lists them.

  • Release ·

    ZcashFoundation zebra 6.2.1

    2 records Highest priority Priority MEDIUM 1 MEDIUM, 1 LOW

    Other records, highest priority first

    • TI-2026-66064 Zebra before 6.2.1 Block Download Denial of Service via KnownBlock SentHashes LockoutPriority LOW 36
    Show all 2 records →

Timeline

  1. 2026-10-02 Threatist record created from CVE-2026-104423
  2. 2026-10-03 Alias added: GHSA-4x5w-56x5-cmfr

References

Advisory 1

  • 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