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chore(deps): update dependency fastify to v5.8.3 [security]#229

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chore(deps): update dependency fastify to v5.8.3 [security]#229
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renovate/npm-fastify-vulnerability

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This PR contains the following updates:

Package Change Age Confidence
fastify (source) 5.6.2 → 5.8.3 age confidence

GitHub Vulnerability Alerts

CVE-2026-25223

Impact

A validation bypass vulnerability exists in Fastify where request body validation schemas specified by Content-Type can be completely circumvented. By appending a tab character (\t) followed by arbitrary content to the Content-Type header, attackers can bypass body validation while the server still processes the body as the original content type.

For example, a request with Content-Type: application/json\ta will bypass JSON schema validation but still be parsed as JSON.

This vulnerability affects all Fastify users who rely on Content-Type-based body validation schemas to enforce data integrity or security constraints. The concrete impact depends on the handler implementation and the level of trust placed in the validated request body, but at the library level, this allows complete bypass of body validation for any handler using Content-Type-discriminated schemas.

This issue is a regression or missed edge case from the fix for a previously reported vulnerability.

Patches

This vulnerability has been patched in Fastify v5.7.2. All users should upgrade to this version or later immediately.

Workarounds

If upgrading is not immediately possible, user can implement a custom onRequest hook to reject requests containing tab characters in the Content-Type header:

fastify.addHook('onRequest', async (request, reply) => {
  const contentType = request.headers['content-type']
  if (contentType && contentType.includes('\t')) {
    reply.code(400).send({ error: 'Invalid Content-Type header' })
  }
})

Resources

CVE-2026-25224

Impact

A Denial of Service vulnerability in Fastify’s Web Streams response handling can allow a remote client to exhaust server memory. Applications that return a ReadableStream (or Response with a Web Stream body) via reply.send() are impacted. A slow or non-reading client can trigger unbounded buffering when backpressure is ignored, leading to process crashes or severe degradation.

Patches

The issue is fixed in Fastify 5.7.3. Users should upgrade to 5.7.3 or later.

Workarounds

Avoid sending Web Streams from Fastify responses (e.g., ReadableStream or Response bodies). Use Node.js streams (stream.Readable) or buffered payloads instead until the project can upgrade.

References

CVE-2026-3635

Summary

When trustProxy is configured with a restrictive trust function (e.g., a specific IP like trustProxy: '10.0.0.1', a subnet, a hop count, or a custom function), the request.protocol and request.host getters read X-Forwarded-Proto and X-Forwarded-Host headers from any connection — including connections from untrusted IPs. This allows an attacker connecting directly to Fastify (bypassing the proxy) to spoof both the protocol and host seen by the application.

Affected Versions

fastify <= 5.8.2

Impact

Applications using request.protocol or request.host for security decisions (HTTPS enforcement, secure cookie flags, CSRF origin checks, URL construction, host-based routing) are affected when trustProxy is configured with a restrictive trust function.

When trustProxy: true (trust everything), both host and protocol trust all forwarded headers — this is expected behavior. The vulnerability only manifests with restrictive trust configurations.

Release Notes

fastify/fastify (fastify)

v5.8.3

Compare Source

⚠️ Security Release

This fixes CVE CVE-2026-3635 GHSA-444r-cwp2-x5xf.

What's Changed

New Contributors

Full Changelog: fastify/fastify@v5.8.2...v5.8.3

v5.8.2

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What's Changed

New Contributors

Full Changelog: fastify/fastify@v5.8.1...v5.8.2

v5.8.1

Compare Source

⚠️ Security Release

Fixes "Missing End Anchor in "subtypeNameReg" Allows Malformed Content-Types to Pass Validation": GHSA-573f-x89g-hqp9.

CVE-2026-3419

Full Changelog: fastify/fastify@v5.8.0...v5.8.1

v5.8.0

Compare Source

What's Changed

New Contributors

Full Changelog: fastify/fastify@v5.7.4...v5.8.0

v5.7.4

Compare Source

Full Changelog: fastify/fastify@v5.7.3...v5.7.4

v5.7.3

Compare Source

⚠️ Security Release
What's Changed

Full Changelog: fastify/fastify@v5.7.2...v5.7.3

v5.7.2

Compare Source

⚠️ Notice ⚠️

Parsing of the content-type header has been improved to a strict parser in PR #​6414. This means only header values in the form described in RFC 9110 are accepted.

What's Changed

New Contributors

Full Changelog: fastify/fastify@v5.7.1...v5.7.2

v5.7.1

Compare Source

What's Changed

Full Changelog: fastify/fastify@v5.7.0...v5.7.1

v5.7.0

Compare Source

What's Changed

New Contributors

Full Changelog: fastify/fastify@v5.6.2...v5.7.0

Configuration

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This PR was generated by Mend Renovate. View the repository job log.

@renovate renovate bot force-pushed the renovate/npm-fastify-vulnerability branch from 0fa6a10 to a8d0095 Compare March 25, 2026 21:16
@renovate renovate bot changed the title chore(deps): update dependency fastify to v5.7.3 [security] chore(deps): update dependency fastify to v5.8.3 [security] Mar 25, 2026
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