CVE-2026-104422 Zebra before 6.3.0 Block Sync Denial of Service via Coinbase scriptSig Rewrite
A malicious peer can delay Zebra node synchronization by serving blocks with manipulated coinbase scriptSigs, causing a denial of service.
- 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-2026-104422?
CVE-2026-104422 is a high-severity denial of service vulnerability in ZcashFoundation zebra, published on 2 Oct 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.
Official description
The block sync download path in Zebra (zebrad) before 6.3.0 reads a block's height from its unvalidated coinbase scriptSig and drops blocks that appear too far behind the tip before consensus validation, without penalizing the supplying peer. Because V5 transaction IDs exclude the scriptSig, a malicious peer can repeatedly serve a canonical block whose coinbase claims height 1 while keeping the requested hash, delaying the node's discovery of the newest block.
Weakness: CWE-345
Which versions are affected by CVE-2026-104422?
How do I fix CVE-2026-104422?
No fix has been published for CVE-2026-104422 yet. Limit exposure of the affected software until one is available.
Upgrade, then put limits on request size, rate and nesting depth so one client cannot exhaust the service. More about Denial of service.
Is CVE-2026-104422 being exploited?
There is no known exploitation of CVE-2026-104422 in the wild and no public exploit code.
Sources
Also known as GHSA-3qff-7hrr-r4g7, GHSA-g95h-hw6g-pvgv.