CVE-2026-104420

MEDIUM 5.3

Zebra before 6.3.0 Peer Misbehavior Ban Bypass via Gossiped Blocks

CVSS Score

5.3

EPSS Score

0.0%

EPSS Percentile

0th

Zebra before 6.3.0 contains a protection mechanism failure that allows unauthenticated peers to evade misbehavior scoring by supplying invalid gossiped blocks. The inbound cleanup step wrongly downcasts RouterError to VerifyBlockError and discards the score, so attackers can repeatedly force block download and Equihash verification without being banned.

CWE	CWE-704
Vendor	zcashfoundation
Product	zebra
Published	Oct 2, 2026

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CVSS v3 Breakdown

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L

Attack Vector

Network

Attack Complexity

Low

Privileges Required

None

User Interaction

None

Scope

Unchanged

Confidentiality

None

Integrity

None

Availability

Low

Affected Versions

ZcashFoundation / zebra

0 < 6.3.0

References

NVD ↗ CVE.org ↗ EPSS Data ↗

github.com: https://github.com/ZcashFoundation/zebra/security/advisories/GHSA-8hh2-hrf2-cqf4 vulncheck.com: https://www.vulncheck.com/advisories/zebra-before-6.3.0-peer-misbehavior-ban-bypass-via-gossiped-blocks

Credits

🔍 evan-forbes