What is CVE-2026-104420?

CVE-2026-104420 is a medium-severity vulnerability in Zcashfoundation Zebra, classified under Incorrect Type Conversion or Cast. CVSS score: 5.3/10. Published 2026-10-02.

How severe is CVE-2026-104420?

Medium severity. CVSS v3 base score is 5.3 out of 10.

Vulnerability in Zcashfoundation Zebra

CVE-2026-104420

Zebra before 6.3.0 contains a protection mechanism failure that allows unauthenticated peers to evade misbehavior scoring by supplying invalid gossiped blocks. The inbound cleanup step wrongly downcasts RouterError to VerifyBlockError and discards the score, so attackers can repeatedly force block download and Equihash verification without being banned.

Published 2026-10-02.

CVSS v3 metric

CVSS v3 base score 5.3 (Medium). Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L.

EPSS exploit prediction

No EPSS score from FIRST.org yet. New CVEs usually get one within a few days; no score means no signal yet, not low risk. How EPSS works.

Affected products

Zcashfoundation Zebra

Weakness classification (CWE)

CWE-704 — Incorrect Type Conversion or Cast

References

github.com/ZcashFoundation/zebra/security/advisories/GHSA-8hh2-hrf2-cqf4 (vendor-advisory)
www.vulncheck.com/advisories/zebra-before-6.3.0-peer-misbehavior-ban-bypass-via… (third-party-advisory)

Frequently asked questions

What is CVE-2026-104420?: CVE-2026-104420 is a medium-severity vulnerability in Zcashfoundation Zebra, classified under Incorrect Type Conversion or Cast. CVSS score: 5.3/10. Published 2026-10-02.
How severe is CVE-2026-104420?: Medium severity. CVSS v3 base score is 5.3 out of 10.