CVE-2026-109366

Zebra before 6.4.0 Gossiped Block Drop via Forged Coinbase scriptSig Height

State: Published
Severity: 6.3 Medium
Published: Oct 12, 2026
Updated: Oct 26, 2026
Reserved: Oct 12, 2026

Description

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.

Scores

CVSS	Score	Vector	Source
4.0	6.3 Medium	CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:N/VI:N/VA:L/SC:N/SI:N/SA:N	VulnCheck
3.1	3.7 Low	CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:L	VulnCheck

Weaknesses

CWE-354 Improper Validation of Integrity Check Value

Affected Products

Product	Versions
zebraZcashFoundation	before 6.4.0Affected 6.4.0Not affected

References

GitHub Security Advisory (GHSA-4f6v-mj46-gxg3)vendor-advisory
VulnCheck Advisory: Zebra before 6.4.0 Gossiped Block Drop via Forged Coinbase scriptSig Heightthird-party-advisory

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