CVE-2026-44499 ZEBRA: Permanent Block Discovery Halt via Gossip Queue Saturation and Syncer Poisoning
An unauthenticated remote attacker can permanently halt block discovery on Zcash nodes by saturating the gossip queue and poisoning the syncer.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Over the internet
- Victim action needed
- Not needed
- Fix
- Available
What is CVE-2026-44499?
CVE-2026-44499 is a high-severity denial of service vulnerability in ZcashFoundation zebra, published on 8 May 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.
Official description
ZEBRA is a Zcash node written entirely in Rust. Prior to version 4.4.0, a composite denial-of-service vulnerability in Zebra's block discovery pipeline allows an unauthenticated remote attacker to permanently halt all new block discovery on a targeted node. The attack exploits three independent weaknesses in the gossip, syncer, and download subsystems — all exercisable from a single TCP connection — to create a monotonically growing block deficit that never self-heals. This issue has been patched in version 4.4.0.
Weakness: CWE-770
Which versions are affected by CVE-2026-44499?
2 open source packages ship an affected version, including zebrad.
| Package | Affected | Fixed in |
|---|---|---|
zebrad crates.io | All versions | 4.4.0 |
zebrad crates.io | All versions | 4.4.0 |
How do I fix CVE-2026-44499?
Upgrade zebrad to 4.4.0 or later.
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-2026-44499 being exploited?
There is no known exploitation of CVE-2026-44499 in the wild and no public exploit code.
Sources
Also known as GHSA-h9hm-m2xj-4rq9.