Zebra before version 7.0.0 contains a CWE-459 weakness (an incomplete cleanup flaw) that lets an unauthenticated peer supply a forged checkpoint block body. By including forged authorizing data close to the final checkpoint, the node receives rejected hashes that remain in the sent-hash set, causing the sync process to halt until the node is restarted. This effectively creates a denial of service during the initial synchronization of the node.

The vulnerability affects the ZcashFoundation Zebra project for all builds prior to version 7.0.0. Any node running a pre‑7.0.0 release and accepting network connections from peers is potentially vulnerable.

The CVSS score of 8.7 indicates a high severity level. Explicit EPSS data is not available, so the exact exploitation probability is unknown, but the flaw can be triggered by any unauthenticated peer. The issue is not yet listed in the CISA KEV catalog. An attacker only needs to forge a checkpoint block body and transmit it to a target node; if the node accepts the forged block, it will cease requesting further blocks until a restart, resulting in an availability outage.