How severe is CVE-2026-54281?

No CVSS score has been assigned to CVE-2026-54281 yet. Review the advisory details and affected package list to assess your exposure.

Which packages are affected by CVE-2026-54281?

CVE-2026-54281 affects the following packages: @nestjs/platform-fastify (npm). Ecosystems affected: npm.

How do I fix CVE-2026-54281?

Update @nestjs/platform-fastify to 11.1.24 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2026-54281 is resolved across your whole dependency graph.

How do I detect CVE-2026-54281 in my npm dependencies?

Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for @nestjs/platform-fastify, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.

How do I mitigate CVE-2026-54281 if there is no patch (or I can't update yet)?

Put an independent control in front of the weakness: restrict the affected endpoint or interface to trusted networks, require an additional authentication factor or proxy-level check, and invalidate existing sessions and credentials in case the flaw has already been used.

Is CVE-2026-54281 actively exploited in the wild?

No public exploit code has been indexed for CVE-2026-54281 yet. This does not mean the vulnerability cannot be exploited — absence of public exploits does not imply safety. Apply the recommended fix and use O3 Security to monitor your exposure.

What is the EPSS score for CVE-2026-54281?

CVE-2026-54281 has an EPSS (Exploit Prediction Scoring System) score of 0.5%, placing it in the 40th percentile of all CVEs. EPSS is maintained by FIRST.org and estimates the probability that a vulnerability will be exploited in the wild within the next 30 days. This score indicates relatively lower exploitation probability, though the CVSS severity should still guide your patching priority.

What type of vulnerability is CVE-2026-54281?

CVE-2026-54281 is classified as CWE-863 (CWE-863). This weakness type describe the underlying flaw category, which helps determine the potential impact and the right class of mitigation.

When was CVE-2026-54281 published, and has it been updated?

CVE-2026-54281 was published on June 22, 2026 and was last updated on August 12, 2026. Advisory data evolves as severity scores, affected ranges, and exploit intelligence are revised — always check the latest version of the advisory before acting.

📦 npm

Not in CISA KEV

CVE-2026-54281 — @nestjs/platform-fastify

CVE-2026-54281 is a CWE-863 vulnerability in @nestjs/platform-fastify. A fix is available for @nestjs/platform-fastify — see the affected versions and patch details below.

Nest: Middleware Bypass on Fastify via Trailing Slash

Also known asGHSA-6v32-fjc9-9qf6

Published

Jun 22, 2026

Updated

Aug 12, 2026

Affected

1 pkg

Patched

1 / 1

Exploits

None indexed

Exploitation data as of Sep 27, 2026 · OSV.dev, NVD, FIRST.org (EPSS)

Exploitation Status

No confirmed exploitation observed yet

A successful exploit gives an attacker total control of the affected component, not partial access.
CISA’s own triage has not observed active exploitation or public proof-of-concept code for this CVE as of its last assessment.

Exploitation and automatability from CISA’s SSVC triage for CVE-2026-54281.

EPSS Exploitation Probability

via FIRST.org ↗

0.5%probability of exploitation in next 30 days

Lower Risk0.00%

Lower risk than most CVEs40th percentile — riskier than 40% of all scored CVEsHighest risk

Probability of exploitation in the next 30 days, from FIRST.org EPSS.

Real-World Exposure

1 pkg affected

How broadly this vulnerability is actually deployed: weekly install volume shows current usage, and reverse-dependency count shows how many other packages break if it stays unpatched.

248other npm packages depend on this — each one inherits the vulnerability until it's patched upstream

@nestjs/platform-fastifynpm

2.0Mdownloads / week

Description

Impact

An authentication bypass vulnerability exists in @nestjs/platform-fastify (confirmed on version 11.1.24, the latest available release at time of report). When middleware is registered through NestJS's MiddlewareConsumer.forRoutes() API on the Fastify adapter, an unauthenticated client can bypass the Nest middleware registered for that route by simply appending a trailing slash (/) to the request URL.

This bypass works on the default Fastify adapter configuration — no special router options need to be enabled. Applications using the standard CRUD route shape (GET /resource and GET /resource/:id) are affected when they protect those routes with MiddlewareConsumer.forRoutes() middleware.

Patches

Fixed in @nestjs/[email protected]

References

Kudos goes to @a-tt-om

Affected Packages

1 total 1 fixed

Ecosystem	Package	Vulnerable range	Fix
📦npm	`@nestjs/platform-fastify`	all versions	11.1.24`npm install @nestjs/platform-fastify@11.1.24`

Detection & mitigation playbook

Open-source dependency

Detect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for @nestjs/platform-fastify, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.
Fix
Update @nestjs/platform-fastify to 11.1.24 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2026-54281 is resolved across your whole dependency graph.
Workarounds
Put an independent control in front of the weakness: restrict the affected endpoint or interface to trusted networks, require an additional authentication factor or proxy-level check, and invalidate existing sessions and credentials in case the flaw has already been used.

Frequently Asked Questions

### Impact An authentication bypass vulnerability exists in `@nestjs/platform-fastify` (confirmed on version `11.1.24`, the latest available release at time of report). When middleware is registered through NestJS's `MiddlewareConsumer.forRoutes()` API on the Fastify adapter, an unauthenticated client can bypass the Nest middleware registered for that route by simply appending a trailing slash (`/`) to the request URL. This bypass works on the **default Fastify adapter configuration** — no special router options need to be enabled. Applications using the standard CRUD route shape (`GET /reso

O3 Security · Impact-Aware SCA

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