CVE-2026-104421
Zebra before 6.2.1 Block Download Denial of Service via KnownBlock SentHashes Lockout
CVSS Score
5.3
EPSS Score
0.0%
EPSS Percentile
0th
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.
| CWE | CWE-459 |
| Vendor | zcashfoundation |
| Product | zebra |
| Published | Oct 2, 2026 |
| Last Updated | 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 < 6.2.1