CVE-2026-123555 Zebra 2.3.0 before 7.0.0 Denial of Service via Unscored Script Verification Failures

High 8.7 Published 8 Nov 2026 Updated 8 Nov 2026

Exploited in the wild: Not known
Fix: None listed

What is CVE-2026-123555?

CVE-2026-123555 is a high-severity vulnerability in ZcashFoundation zebra, published on 8 Nov 2026.

Official description

Zebra from 2.3.0 before 7.0.0 contains a denial of service vulnerability that allows unauthenticated peers to evade misbehavior scoring by sending transactions or blocks with invalid transparent scripts. Attackers can flood mempool with script-failing transactions or serve forged v5 block bodies with altered scriptSig bytes to exhaust CPU and repeatedly stall block sync.

Weakness: CWE-755

Which versions are affected by CVE-2026-123555?

How do I fix CVE-2026-123555?

No fix has been published for CVE-2026-123555 yet. Limit exposure of the affected software until one is available.

Is CVE-2026-123555 being exploited?

There is no known exploitation of CVE-2026-123555 in the wild and no public exploit code.

Sources

Also known as GHSA-cwcw-qfgm-5r6m, GHSA-jq45-ghw5-v37x.