CVE-2026-104420 Zebra before 6.3.0 Peer Misbehavior Ban Bypass via Gossiped Blocks
Attackers can bypass peer misbehavior bans in Zebra by sending invalid gossiped blocks, enabling repeated resource-intensive verification attempts.
- 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-2026-104420?
CVE-2026-104420 is a medium-severity 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
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.
Weakness: CWE-704
Which versions are affected by CVE-2026-104420?
How do I fix CVE-2026-104420?
No fix has been published for CVE-2026-104420 yet. Limit exposure of the affected software until one is available.
Is CVE-2026-104420 being exploited?
There is no known exploitation of CVE-2026-104420 in the wild and no public exploit code.
Sources
Also known as GHSA-8hh2-hrf2-cqf4, GHSA-hfc4-gh7c-43q2.