What is CVE-2026-123554?

CVE-2026-123554 is a high-severity vulnerability in Zcashfoundation Zebra, classified under Inefficient Algorithmic Complexity. CVSS score: 7.5/10. Published 2026-11-08.

How severe is CVE-2026-123554?

High severity. CVSS v3 base score is 7.5 out of 10.

Vulnerability in Zcashfoundation Zebra

CVE-2026-123554

Zebra zebrad 6.4.0 before 7.0.0 performs quadratic work in the mempool coinbase-maturity check because Transaction::coinbase_spend_restriction() rebuilds the transaction's output list once per spent outpoint. Any connected peer can repeatedly send unsigned transactions with many transparent inputs and outputs, which are rejected without a misbehavior score, to pin verification threads.

Published 2026-11-08 · last modified 2026-11-09.

CVSS v3 metric

CVSS v3 base score 7.5 (High). Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H.

EPSS exploit prediction

EPSS: 0.004 (37.7th percentile), scored 2026-11-09.

Very low probability of exploitation in the next 30 days; routine patching cadence is appropriate. 38th percentile — 37.7% of CVEs in the catalogue have a lower EPSS than this one. How to read EPSS.

The 30-day trend appears once there are two daily scores.

Affected products

Zcashfoundation Zebra

Weakness classification (CWE)

CWE-407 — Inefficient Algorithmic Complexity

References

github.com/ZcashFoundation/zebra/commit/08743d669b33a19bce2a5d54001bd468c03a196e (patch)
github.com/ZcashFoundation/zebra/security/advisories/GHSA-7jp4-mq53-4cvq (vendor-advisory)
www.vulncheck.com/advisories/zebra-zebrad-6.4.0-before-7.0.0-denial-of-service-… (third-party-advisory)

Frequently asked questions

What is CVE-2026-123554?: CVE-2026-123554 is a high-severity vulnerability in Zcashfoundation Zebra, classified under Inefficient Algorithmic Complexity. CVSS score: 7.5/10. Published 2026-11-08.
How severe is CVE-2026-123554?: High severity. CVSS v3 base score is 7.5 out of 10.