CVE-2026-109366: Improper Validation of Integrity Check Value in ZcashFoundation zebra
Description
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.
CVSS v4.0
Score 6.3medium
Affected software
ZcashFoundation
zebra
pkg:github/zcashfoundation/zebraRun on your own infrastructure? Check whether these packages are installed with threat-finder — our free open-source scanner.
AI-Powered Analysis
Machine-generated threat intelligence
Technical Analysis
CVE-2026-109366 describes an improper validation of integrity check values in Zebra before version 6.4.0. Specifically, unauthenticated peers can exploit the inbound gossip download path by serving a legitimate block whose coinbase scriptSig is rewritten to height 1 while preserving the ZIP-244 block hash. This causes the system to drop new blocks prematurely before consensus validation, delaying tip discovery for mining backends and potentially impacting blockchain synchronization.
Potential Impact
The vulnerability allows unauthenticated attackers to disrupt block propagation by forcing the dropping of new blocks without penalty. This can delay tip discovery for mining backends, potentially affecting blockchain synchronization and mining operations. There is no indication of direct consensus compromise or chain reorganization, but the delay could impact network performance and mining efficiency.
Mitigation Recommendations
A fix is available in Zebra version 6.4.0. Users should upgrade to version 6.4.0 or later to remediate this vulnerability. Patch status is confirmed by the affectedVersions field indicating versions before 6.4.0 are vulnerable.
Technical Details
- Data Version
- 5.2
- Assigner Short Name
- VulnCheck
- Date Reserved
- 2026-10-12T14:21:32.595Z
- Cvss Version
- 4.0
- State
- PUBLISHED
Threat ID: 6acd0c192cdf04f656b11c1d
Added to database: 10/12/2026, 16:34:33 UTC
Last enriched: 10/12/2026, 16:48:42 UTC
Last updated: 10/12/2026, 21:46:36 UTC
Views: 12
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