What is CVE-2026-109366?

CVE-2026-109366 is a low-severity vulnerability in Zcashfoundation Zebra, classified under Improper Validation of Integrity Check Value. CVSS score: 3.7/10. Published 2026-10-12.

How severe is CVE-2026-109366?

Low severity. CVSS v3 base score is 3.7 out of 10.

Vulnerability in Zcashfoundation Zebra

CVE-2026-109366

Zebra before 6.4.0 contains an improper integrity validation vulnerability in the inbound gossip download path that allows unauthenticated peers to force dropping of new blocks without penalty. Attackers can serve a real block with a coinbase scriptSig rewritten to height 1, which keeps the ZIP-244 block hash, triggering a behind-tip drop before consensus validation and delaying tip discovery for mining backends.

Published 2026-10-12.

CVSS v3 metric

CVSS v3 base score 3.7 (Low). Vector: CVSS:3.1/AV:N/AC:H/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-354 — Improper Validation of Integrity Check Value

References

github.com/ZcashFoundation/zebra/security/advisories/GHSA-4f6v-mj46-gxg3 (vendor-advisory)
www.vulncheck.com/advisories/zebra-before-6.4.0-gossiped-block-drop-via-forged-… (third-party-advisory)

Frequently asked questions

What is CVE-2026-109366?: CVE-2026-109366 is a low-severity vulnerability in Zcashfoundation Zebra, classified under Improper Validation of Integrity Check Value. CVSS score: 3.7/10. Published 2026-10-12.
How severe is CVE-2026-109366?: Low severity. CVSS v3 base score is 3.7 out of 10.