# CVE-2026-123556: Zebra 4.5.0 before 7.0.0 Honest Peer Ban via Mempool Lock-Time Scoring

Status: published. Published: 2026-11-08. Updated: 2026-11-12.

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.

## Remediation

No remediation reported in collected sources

## Affected products and versions

- ZcashFoundation / zebra (zebrad): ≥ 4.5.0; < 7.0.0 (affected, semver); 7.0.0 (unaffected, semver). Source: CNA: VulnCheck

## Severity and prioritization

- CVSS 4.0: 6.9 (medium); CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:L/SC:N/SI:N/SA:N; source: CNA: VulnCheck

- CVSS 3.1: 5.3 (medium); CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L; source: CNA: VulnCheck

- CVSS 4.0: 6.9 (medium); CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:L/SC:N/SI:N/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X; source: NVD: disclosure@vulncheck.com

- CVSS 3.1: 5.3 (medium); CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L; source: NVD: disclosure@vulncheck.com

- CISA KEV: No listing in collected sources

- EPSS: 0.30% as of 2026-11-10; percentile 23.44%

- SSVC: exploitation none; automatable yes; technical impact partial; source ADP: CISA-ADP

- Weaknesses: CWE-693

## Exploit evidence

No exploit evidence in collected sources. This is not proof of no exploitation.

## References

- https://github.com/ZcashFoundation/zebra/security/advisories/GHSA-5h3r-fpmj-483w (CNA: VulnCheck; vendor-advisory)

- https://www.vulncheck.com/advisories/zebra-4.5.0-before-7.0.0-honest-peer-ban-via-mempool-lock-time-scoring (CNA: VulnCheck; third-party-advisory)

- https://github.com/ZcashFoundation/zebra/security/advisories/GHSA-5h3r-fpmj-483w (disclosure@vulncheck.com)

- https://www.vulncheck.com/advisories/zebra-4.5.0-before-7.0.0-honest-peer-ban-via-mempool-lock-time-scoring (disclosure@vulncheck.com)

## Provenance

- CNA: VulnCheck: https://www.cve.org/CVERecord?id=CVE-2026-123556; retrieved 2026-11-12; source updated 2026-11-12

- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-123556; retrieved 2026-11-08; source updated 2026-11-08

- FIRST EPSS: https://api.first.org/data/v1/epss?cve=CVE-2026-123556; retrieved 2026-11-11; source updated Not reported

Revision: 600f907afdf84e4973b2ce4fe4a2d55ddd05f76daeab8d086423ef7934f0d0fe

Canonical: https://y2.dev/cve/CVE-2026-123556

## Agent and API access

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- Cyber API: https://api.y2.dev/api/v2/cyber/cves and https://api.y2.dev/api/v2/cyber/cves/{cveId}.

- Y2 Pro or Elite: create a workspace API key with the intel:cyber scope and send Authorization: Bearer <Y2_API_KEY>. Setup: https://y2.dev/docs/api/create-key.

- x402: Pay per request without an account or API key. Omit Authorization, read the HTTP 402 PAYMENT-REQUIRED challenge, validate its current requirements, and retry with PAYMENT-SIGNATURE through an authorized payment client. These browser tools never make payments. Guide: https://y2.dev/docs/api/x402.

- OpenAPI: https://y2.dev/api/openapi.yaml. Agent access metadata: https://y2.dev/cve/agent.json.

Collected public records only. Check source status for coverage and freshness.