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TI-2026-66064 Aliases CVE-2026-104421GHSA-xx63-6p6j-3wv7

Zebra before 6.2.1 Block Download Denial of Service via KnownBlock SentHashes Lockout

Priority LOW 36CWE-459Published · 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 · Low
Fix status
Fixed

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

Summary

Zebra before 6.2.1 contains an incomplete cleanup vulnerability that allows unauthenticated peers to block downloading of valid blocks by leaving rejected hashes in SentHashes. Attackers can send a contextually invalid block sharing an honest block's header hash, causing Request::KnownBlock to skip the honest block and keep nodes behind the tip.

Why it matters now

Exploitation None reported CISA SSVC · not in CISA KEV
EPSS 0.00304 23rd 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-2026-66066 Zebra before 6.2.1 Denial of Service via Uncapped V6 Shielded Proof VerificationPriority MEDIUM 44
    Show all 2 records →

Timeline

  1. 2026-10-02 Threatist record created from CVE-2026-104421
  2. 2026-10-03 Alias added: GHSA-xx63-6p6j-3wv7

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-2026-30136 ZEBRA: Consensus Divergence in Transparent Sighash Hash-Type Handling CVSS 4.0CRITICAL 9.3
  • TI-2026-37853 ZEBRA: Consensus divergence via P2SH sigop undercount in pure-Rust disabled-opcode parser CVSS 4.0CRITICAL 9.3
See all 44 →

Sources

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