High severity · published Oct 2, 2026
CVE-2026-104423
Zebra before 6.2.1 Denial of Service via Uncapped V6 Shielded Proof Verification
7.5
CVSS
0.3%
EPSS
No
On KEV
Description
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 vector
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
Attack vector
Network
Complexity
Low
Privileges
None
User interaction
None
Confidentiality
None
Integrity
None
Availability
High
Scope
Unchanged
Exploitation
Is it being used?
Exploit prediction (EPSS)0.3% · higher than 28% of CVEs
Exploited in the wildNo evidence yet
CISA KEVNot listed
Ransomware campaign useNot known
Affected products
Which versions
ZE
zebra · ZcashFoundation
before 6.2.1 · source: vendor
References
NVD
https://nvd.nist.gov/vuln/detail/CVE-2026-104423
CVE.org
https://www.cve.org/CVERecord?id=CVE-2026-104423
vendor-advisory
https://github.com/ZcashFoundation/zebra/security/advisories/GHSA-2p4c-3q4q-p463
third-party-advisory
https://www.vulncheck.com/advisories/zebra-before-6.2.1-denial-of-service-via-uncapped-v6-shielded-proof-verification
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