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TI-2026-71182 Aliases CVE-2026-109366GHSA-mprq-2cjh-7qc2

Improper block validation in Zebra gossip lets peers drop new blocks

Priority MEDIUM 61CWE-354Published · Updated

Key facts

Attack vector
Network
Privileges required
None
User interaction
None
Attack complexity
Low
Attack requirements
Present
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 6.4.0 from ZcashFoundation has an improper integrity validation flaw in its inbound gossip block download path, tracked as CWE-354. An unauthenticated peer can serve a real block with a rewritten coinbase scriptSig height, which keeps the block hash valid and forces the node to drop new blocks without penalty. Tip discovery is delayed for mining backends. The vulnerability is rated CVSS 4.0 Medium, and CISA SSVC data reports a proof of concept exists and that the issue is not automatable.

Written with Claude Haiku 5.5 from the sources below · 2026-10-29

Description from the CNA

Zebra before 6.4.0 contains an improper integrity validation vulnerability in the inbound gossip download path that allows unauthenticated peers to force dropping of new blocks without penalty. Attackers can serve a real block with a coinbase scriptSig rewritten to height 1, which keeps the ZIP-244 block hash, triggering a behind-tip drop before consensus validation and delaying tip discovery for mining backends.

Why it matters now

Exploitation Proof of concept CISA SSVC · not in CISA KEV
EPSS 0.00157 4th percentileScored 2026-11-07
Fix Fixed zebra (ZcashFoundation): 6.4.0

SSVC decision points

CISA ADP · SSVC 2.0.3

Exploitation
Poc
Automatable
No
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 6.4.06.4.0Patch availableCNA
  • zebra VendorZcashFoundation Affected before 6.4.0 Fixed in 6.4.0 Patch available CNA

Remediation

Upgrade ZcashFoundation Zebra to version 6.4.0 or later. The sources list no advisory identifier for this fix.

Written with Claude Haiku 5.5 from the sources below · 2026-10-29

  • Fix · CNA zebra (ZcashFoundation) Fixed in 6.4.0

Fixed in the same release

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

  • Release ·

    ZcashFoundation zebra 6.4.0

    3 records Highest priority Priority MEDIUM 1 MEDIUM, 2 LOW

    Other records, highest priority first

    • TI-2026-71180 Peer ban bypass in Zcash Zebra via exact-IP ban keyingPriority LOW 36
    • TI-2026-71181 Zebra accepts forged block bodies, enabling denial of servicePriority LOW 27
    Show all 3 records →

Timeline

  1. 2026-10-12 Threatist record created from CVE-2026-109366
  2. 2026-10-12 Alias added: GHSA-mprq-2cjh-7qc2
  3. 2026-10-13 Priority changed: MEDIUM → LOW
  4. 2026-10-26 CISA SSVC decision points changed
  5. 2026-10-26 Priority changed: LOW → MEDIUM

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-2026-29537 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
  • TI-2026-86700 Improper cleanup stalls Zebra checkpoint sync via a malicious peer 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