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CVE-2026-104422GHSA-g95h-hw6g-pvgv

Zebra before 6.3.0 Block Sync Denial of Service via Coinbase scriptSig Rewrite

ZcashFoundation zebra
Open in ThreatlineRecord JSON
CVSS
8.7High
ExploitationNo known exploitationNot in CISA KEV, which does not prove it is unexploitedCISA KEV
Exploit odds (EPSS)0.18%Chance of exploitation activity in the next 30 days, higher than 7% of CVEs. Scored 23 Oct 2026FIRST EPSS
Fixed in6.3.0Fixed 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

The block sync download path in Zebra (zebrad) before 6.3.0 reads a block's height from its unvalidated coinbase scriptSig and drops blocks that appear too far behind the tip before consensus validation, without penalizing the supplying peer. Because V5 transaction IDs exclude the scriptSig, a malicious peer can repeatedly serve a canonical block whose coinbase claims height 1 while keeping the requested hash, delaying the node's discovery of the newest block.

Text from CVE List

Affected versions 2

  • zebraaffected: all versions before 6.3.0CVE List
  • zebraunaffected: 6.3.0CVE List

References 2