CVE-2026-18500

HIGHPre-NVD 8.18.1—
EchelonGraph scoreMEDIUM confidence

This high-severity CVE scores 8.1 under a secondary CVSS source (NVD's own analysis pending). EPSS exploit probability: 0.3% (15th percentile of EPSS-scored CVEs). 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
8.1EG
EchelonGraph verdictPlan mitigationSerious severity, but no confirmed exploitation yet.
  • High severity, but no confirmed exploitation yet
CISA-KEV: Not listedEPSS PROB: 0.3%CVSS: 8.1Exploit: None knownExposed services: Not assessed

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

@fastify/jwt is a JSON Web Token plugin for Fastify. In versions before 10.2.2, a per-request verification key passed to request.jwtVerify({ key }) is silently overridden by the plugin's globally configured secret, because the option merge applies the global key last. Applications that use different keys for different authorization domains, for example separate user and admin keys, therefore accept a token signed with the global key on a route that explicitly requires another key. This lets an ordinary authenticated user cross a key-based trust boundary without knowing either secret. The issue is fixed in @fastify/jwt 10.2.2, where an explicit per-call key takes precedence over the global secret. Users should upgrade to 10.2.2.

CVSS v3
8.1
EG Score
8.1HIGHmedium confidence
EG Risk
37
EG Risk 37/100CISA SSVC

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
Severity81% × 45%
Exploitation0% × 40%
Automatability0% × 15%
CISA SSVC: Track at low or medium mission impact; Track* at high (mission-essential systems).
Action: No fix is confirmed yet. Restrict network exposure of the affected system or apply the vendor's mitigation within your standard update timelines, and watch the vendor's advisory for the fix.
EPSS PROB
0.3%
EPSS %ILE
15th
KEV
Not listed

CISA SSVCTrack at low or medium mission impact; Track* at high (mission-essential systems).

No fix is confirmed yet. Restrict network exposure of the affected system or apply the vendor's mitigation within your standard update timelines, and watch the vendor's advisory for the fix.

Exploitation none (CISA Vulnrichment) · Automatable no (CISA Vulnrichment) · Technical impact total (CISA Vulnrichment). Mission impact is CISA's Mission & Well-being decision point, and only you can judge it: high means the affected system is essential to your organisation's mission, or its compromise could cause irreversible harm to people. CISA's decision table

Published

August 15, 2026

Last Modified

September 4, 2026

Advisory Details (2)

Auto-updated Aug 15, 2026
No fix on record yet. Sources: github.
generic

Security Advisories | OpenJS Foundation CVE Numbering Authority

https://cna.openjsf.org/security-advisories.html
githubMentions a patch (unverified)

@fastify/jwt vulnerable to authorization bypass via global secret overriding the per-request key · Advisory · fastify/fastify-jwt · GitHub

https://github.com/fastify/fastify-jwt/security/advisories/GHSA-j4cx-787j-xjqg

Weakness Classification(1)

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

Data Freshness Timeline

(refreshed 10× in last 7d / 43× 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. 2026-10-10 19:59 UTCEPSS rescore
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  1. 2026-09-22 15:45 UTCEG score recompute
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  63. 2026-08-15 14:29 UTCEG score recompute
  64. 2026-08-15 13:28 UTCEG score recompute
  65. 2026-08-15 13:26 UTCMITRE cvelistV5first tracked

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Frequently asked(5)

What is CVE-2026-18500?
CVE-2026-18500 is a high vulnerability published on August 15, 2026. @fastify/jwt is a JSON Web Token plugin for Fastify. In versions before 10.2.2, a per-request verification key passed to request.jwtVerify({ key }) is silently overridden by the plugin's globally configured secret, because the option merge applies the global key last. Applications that use…
When was CVE-2026-18500 disclosed?
CVE-2026-18500 was first published on August 15, 2026, with the most recent update on September 4, 2026. EchelonGraph re-ingests CVE updates from NVD on a 2-hour cycle, so this page reflects the latest published state.
Is CVE-2026-18500 actively exploited?
CVE-2026-18500 is not currently on CISA's Known Exploited Vulnerabilities catalog. FIRST EPSS estimates a 0.3% probability of exploitation in the next 30 days (15th percentile of EPSS-scored CVEs).
What is the CVSS score of CVE-2026-18500?
CVE-2026-18500 has a CVSS base score of 8.1 (a secondary CVSS source that NVD displays; NVD's own analysis pending).
How do I remediate CVE-2026-18500?
No fix for CVE-2026-18500 is confirmed yet. Until one is published, restrict network exposure of the affected system or apply the vendor's mitigation — for example, keep it off the internet or limit it to trusted networks — and watch the vendor's advisory for the fix.

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