CVE-2026-104423

Zebra (zebrad) before 6.2.1 contains an asymmetric resource consumption vulnerability that allows unauthenticated peers to stall block verification by pushing V6 mempool transactions with invalid Halo2 proofs. Attackers can flood the shared unprioritized Halo2 verification queue with zero-fee transactions carrying zero-filled Orchard and Ironwood proofs, causing nodes to fall behind the chain tip.

CVSS 4.0

8.7CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N

CVSS 3.1

7.5CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

EPSS

0.3% chance of exploitation in the next 30 days; higher than 27% of CVEs (scores of 2026-10-25)

CWE

CWE-405

Published

2026-10-02

Modified

2026-10-02

Record from

the NVD, synced 2026-10-19

References

• https://github.com/ZcashFoundation/zebra/security/advisories/GHSA-2p4c-3q4q-p463
• https://www.vulncheck.com/advisories/zebra-before-6.2.1-denial-of-service-via-uncapped-v6-shielded-proof-verification

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