CVE-2026-109365 Zebra before 6.4.0 Denial of Service via Same-Hash Forged Block Bodies
Unauthenticated attackers can cause denial of service in Zebra nodes by serving forged block bodies that trigger expensive proof verification.
- 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-2026-109365?
CVE-2026-109365 is a medium-severity denial of service 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 uncontrolled resource consumption vulnerability that allows unauthenticated peers to force full proof verification by serving forged block bodies with valid header hashes. Attackers can flip authorizing-only bytes such as a coinbase scriptSig, wasting Sapling, Orchard, and Ironwood proof verification without penalty and stalling sync for 67 seconds.
Weakness: CWE-345
Which versions are affected by CVE-2026-109365?
How do I fix CVE-2026-109365?
No fix has been published for CVE-2026-109365 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-2026-109365 being exploited?
There is no known exploitation of CVE-2026-109365 in the wild and no public exploit code.
Sources
Also known as GHSA-3c94-hf7p-g5mf, GHSA-q5ww-8rv8-j2cv.