Quick answers
- Is CVE-2026-123557 exploited in the wild?
- No. Junglewise Threat Intelligence has no report of CVE-2026-123557 being exploited in the wild.
- How severe is CVE-2026-123557?
- Medium severity, with a CVSS score of 5.9, published 8 November 2026.
- Which products and versions are affected?
- Zcash Foundation Zebra before 7.0.0.
- Is there a fix for CVE-2026-123557?
- Yes: fixed in 7.0.0. Until then: Run zebrad under a process supervisor with automatic restart capability (such as systemd with Restart=on-failure, or a container restart policy) to limit outage duration when the process aborts. Junglewise finds every place you run it, drafts the upgrade and applies it once you approve.
- How is CVE-2026-123557 attacked?
- It is attacked over the network.
- Am I affected by CVE-2026-123557?
- Check whether you run Zcash Foundation Zebra at an affected version. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.
How to fix
- Fixed in: 7.0.0
Run zebrad under a process supervisor with automatic restart capability (such as systemd with Restart=on-failure, or a container restart policy) to limit outage duration when the process aborts.
Technical details
The vulnerability is a reachable assertion in the peer connection handler (CWE-617, CWE-362). When a peer disconnects while zebrad is blocked writing an outbound message to that peer's socket, a MustUseClientResponseSender is dropped without being resolved, triggering an assert! that aborts the process (release builds use panic="abort"). An unauthenticated peer can trigger this by returning empty FindBlocks/FindHeaders replies and stopping socket reads during node synchronization.
Affected products
- Zcash Foundation Zebra before 7.0.0
Timeline
- 2026-10-22: disclosed
- 2026-10-22: patched: version 7.0.0 released
- 2026-11-08: advisory