CVE-2026-89420

HIGHPre-NVD 7.17.1—
EchelonGraph scoreMEDIUM confidence

This high-severity CVE scores 7.1 under a secondary CVSS source (NVD's own analysis pending). EPSS exploit probability: 0.5%, top 62% of all CVEs by exploit prediction. GitHub Security Advisory data not yet ingested — confidence will rise once GHSA publishes (typical lag: hours to days for open-source ecosystem CVEs; never for infrastructure-only CVEs).

Triggered by: NVD CVSS baseline
Sources: epss, secondary
Trending — 4 sources updated this weekElevated
7.1EG
EchelonGraph verdictPlan a fixSerious severity, but no confirmed exploitation yet.
  • High severity, but no confirmed exploitation yet
CISA-KEV: Not listedEPSS PROB: 0%CVSS: 7.1Exploit: Elevated riskExposed: 0

No vendor fix yet — apply a workaround or compensating control (WAF / firewall / segmentation) and watch for a patch.

Improper Validation of Specified Quantity in Input in ZenHive mpp allows a client holding an open payment channel to obtain paid resources without being charged.

MPP.Session.Actions.accept_voucher/3 in lib/mpp/session/actions.ex treats a voucher whose cumulativeAmount equals the channel's already-accepted cumulative amount as an idempotent success, returning the channel unchanged without calling maybe_spend/2. The credential verifies, the protected resource is served, and spent and units stay where they were. Because the server issues a fresh challenge per request and the credential replay store keys on challenge id and payload, the same signed voucher can be re-presented under every new challenge, so one paid voucher yields an unbounded number of paid units. The path is reachable from any method built on MPP.Session.Method through the Plug, MCP, JSON-RPC and WebSocket transports.

This issue affects mpp: from 0.14.0 before 0.16.2.

CVSS v3
7.1
EG Score
7.1(medium)
EG Risk
48(Track)
EG Risk 48/100SSVC: Track

EG Risk is EchelonGraph's 0–100 priority score: it fuses intrinsic severity with real-world exploitation and automatability so you can rank equal-severity CVEs and fix the most dangerous first. Higher = act sooner. Distinct from the 0–10 EG Score (severity).

How it’s computed
Severity71% × 45%
Exploitation40% × 40%
Automatability0% × 15%
Action: Routine — remediate on your standard cadence.
EPSS PROB
0%
EPSS %ILE
38%
KEV
Not listed

Published

September 22, 2026

Last Modified

September 22, 2026

Advisory Details (5)

Auto-updated Sep 22, 2026
Patch available. Sources: github, github_commit.
github_commit

commit 7270edc1dcfb (ZenHive/mpp)

Fix landed in ZenHive/mpp commit 7270edc1dcfb — awaiting tagged release

https://github.com/ZenHive/mpp/commit/7270edc1dcfb58250cc5ee812876609206564165
github_commit

commit 82df569c898b (ZenHive/mpp)

Fix landed in ZenHive/mpp commit 82df569c898b — awaiting tagged release

https://github.com/ZenHive/mpp/commit/82df569c898be1137189e3648e1edb4af6363651
generic

OSV - Open Source Vulnerabilities

https://osv.dev/vulnerability/EEF-CVE-2026-89420
generic

CVE-2026-89420

https://cna.erlef.org/cves/CVE-2026-89420.html
github Patch Available

Session voucher that adds no new funds is accepted and the request is served without a charge — unlimited free units after one paid voucher · Advisory · ZenHive/mpp · GitHub

https://github.com/ZenHive/mpp/security/advisories/GHSA-8c63-r789-xrrf

Vendor Advisories for CVE-2026-89420(1)

These vendors published their own advisory mentioning this CVE — often with vendor-specific remediation steps + affected product lists not in NVD.

Affected Packages

(1 across 1 ecosystem)
Hex(1)
PackageVulnerable rangeFixed inDependents
mpp0.14.0, 0.15.0, 0.16.0, 0.16.10.16.2—

Weakness Classification(1)

MITRE Common Weakness Enumeration — the root-cause categories this CVE belongs to.

Data Freshness Timeline

(refreshed 14× in last 7d / 14× in last 30d)

Each row is a source pipeline that fetched or updated this CVE on that date, with what changed. For example, "NVD update" means NVD published or revised its analysis for this CVE; "MITRE cvelistV5" means we ingested or refreshed it from the CNA feed. Most recent first.

  1. 2026-09-24 22:58 UTCEG score recompute
  2. 2026-09-24 22:58 UTCGHSA enrichment
  3. 2026-09-24 14:04 UTCEPSS rescore
  4. 2026-09-24 09:57 UTCGHSA enrichment
  5. 2026-09-23 21:02 UTCEG score recompute
  6. 2026-09-23 21:02 UTCGHSA enrichment
  7. 2026-09-23 17:54 UTCEPSS rescore
  8. 2026-09-23 08:07 UTCGHSA enrichment
  9. 2026-09-22 19:12 UTCGHSA enrichment
  10. 2026-09-22 13:18 UTCEG score recompute
  11. 2026-09-22 13:18 UTCGHSA enrichment
  12. 2026-09-22 12:22 UTCEG score recompute
  13. 2026-09-22 11:21 UTCEG score recompute
  14. 2026-09-22 11:20 UTCMITRE cvelistV5first tracked

Related CVEs(same product + same CWE)

Frequently asked(5)

What is CVE-2026-89420?
CVE-2026-89420 is a high vulnerability published on September 22, 2026. Improper Validation of Specified Quantity in Input in ZenHive mpp allows a client holding an open payment channel to obtain paid resources without being charged. MPP.Session.Actions.acceptvoucher/3 in lib/mpp/session/actions.ex treats a voucher whose cumulativeAmount equals the channel's…
When was CVE-2026-89420 disclosed?
CVE-2026-89420 was first published in the National Vulnerability Database on September 22, 2026. EchelonGraph re-ingests CVE updates from NVD on a 2-hour cycle, so this page reflects the latest published state.
Is CVE-2026-89420 actively exploited?
CVE-2026-89420 is not currently on CISA's Known Exploited Vulnerabilities catalog. FIRST EPSS estimates a 0% probability of exploitation in the next 30 days, which ranks it in the top 62.4% of all scored CVEs.
What is the CVSS score of CVE-2026-89420?
CVE-2026-89420 has a CVSS v3 base score of 7.1 (NVD).
How do I remediate CVE-2026-89420?
Patch to the fixed version published by the affected vendor. Where vendor advisories exist for CVE-2026-89420, EchelonGraph cross-links them in the Vendor Advisories panel below — those typically contain the canonical remediation steps, fixed version numbers, and any vendor-specific mitigations.

Dependency Blast Radius

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