CVE-2026-109366 Zebra before 6.4.0 Gossiped Block Drop via Forged Coinbase scriptSig Height
Attackers can force Zebra nodes to drop valid blocks by forging coinbase heights, delaying tip discovery and causing denial of service for mining backends.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Over the internet
- Victim action needed
- Not needed
- Fix
- None listed
What is CVE-2026-109366?
CVE-2026-109366 is a medium-severity vulnerability in ZcashFoundation zebra, published on 12 Oct 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.
Official 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.
Weakness: CWE-354
Which versions are affected by CVE-2026-109366?
How do I fix CVE-2026-109366?
No fix has been published for CVE-2026-109366 yet. Limit exposure of the affected software until one is available.
Is CVE-2026-109366 being exploited?
It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-109366 exists.
Sources
Also known as GHSA-4f6v-mj46-gxg3, GHSA-mprq-2cjh-7qc2.