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CVE-2026-104421GHSA-x93j-mj2f-q338

Zebra before 6.2.1 Block Download Denial of Service via KnownBlock SentHashes Lockout

ZcashFoundation zebra
Open in ThreatlineRecord JSON
CVSS
6.9Medium
ExploitationNo known exploitationNot in CISA KEV, which does not prove it is unexploitedCISA KEV
Exploit odds (EPSS)0.30%Chance of exploitation activity in the next 30 days, higher than 22% of CVEs. Scored 23 Oct 2026FIRST EPSS
Fixed in6.2.1Fixed versionCVE List
Published2 Oct 2026Updated 2 Oct 2026CVE List

What fixes it

A fixed version on one release line is not the upgrade target for every line. Check your exact version and any vendor backports.

Description

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.

Text from CVE List

Affected versions 2

  • zebraaffected: all versions before 6.2.1CVE List
  • zebraunaffected: 6.2.1CVE List

References 2