Medium severity · published Oct 2, 2026
CVE-2026-104420
Zebra before 6.3.0 Peer Misbehavior Ban Bypass via Gossiped Blocks
5.3
CVSS
0.3%
EPSS
No
On KEV
Description
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.
CVSS vector
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L
Attack vector
Network
Complexity
Low
Privileges
None
User interaction
None
Confidentiality
None
Integrity
None
Availability
Low
Scope
Unchanged
Exploitation
Is it being used?
Exploit prediction (EPSS)0.3% · higher than 23% of CVEs
Exploited in the wildNo evidence yet
CISA KEVNot listed
Ransomware campaign useNot known
Affected products
Which versions
ZE
zebra · ZcashFoundation
before 6.3.0 · source: vendor
References
NVD
https://nvd.nist.gov/vuln/detail/CVE-2026-104420
CVE.org
https://www.cve.org/CVERecord?id=CVE-2026-104420
vendor-advisory
https://github.com/ZcashFoundation/zebra/security/advisories/GHSA-8hh2-hrf2-cqf4
third-party-advisory
https://www.vulncheck.com/advisories/zebra-before-6.3.0-peer-misbehavior-ban-bypass-via-gossiped-blocks
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