What is CVE-2026-123556?

CVE-2026-123556 is a medium-severity vulnerability in Zcashfoundation Zebra, classified under Protection Mechanism Failure. CVSS score: 5.3/10. Published 2026-11-08.

How severe is CVE-2026-123556?

Medium severity. CVSS v3 base score is 5.3 out of 10.

Vulnerability in Zcashfoundation Zebra

CVE-2026-123556

ZcashFoundation Zebra from 4.5.0 before 7.0.0 contains a protection mechanism failure that bans honest peers by scoring mempool lock-time rejections at the ban threshold. Attackers can broadcast transactions locked until the current height right after each block, causing lagging nodes to ban honest relaying peers for 24 hours or until restart.

Published 2026-11-08 · last modified 2026-11-08.

CVSS v3 metric

CVSS v3 base score 5.3 (Medium). Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L.

EPSS exploit prediction

No EPSS score from FIRST.org yet. New CVEs usually get one within a few days; no score means no signal yet, not low risk. How EPSS works.

Affected products

Zcashfoundation Zebra

Weakness classification (CWE)

CWE-693 — Protection Mechanism Failure

References

GitHub Security Advisory (GHSA-5h3r-fpmj-483w) (vendor-advisory)
VulnCheck Advisory: Zebra 4.5.0 before 7.0.0 Honest Peer Ban via Mempool Lock-Time Scoring (third-party-advisory)

Frequently asked questions

What is CVE-2026-123556?: CVE-2026-123556 is a medium-severity vulnerability in Zcashfoundation Zebra, classified under Protection Mechanism Failure. CVSS score: 5.3/10. Published 2026-11-08.
How severe is CVE-2026-123556?: Medium severity. CVSS v3 base score is 5.3 out of 10.