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chore(deps): update dependency fastify to v5.8.5 [security]#342

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chore(deps): update dependency fastify to v5.8.5 [security]#342
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renovate/npm-fastify-vulnerability

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@renovate renovate Bot commented Mar 5, 2026 •
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This PR contains the following updates:

Package Change Age Confidence
fastify (source) 5.7.4 → 5.8.5 age confidence

Fastify's Missing End Anchor in "subtypeNameReg" Allows Malformed Content-Types to Pass Validation

CVE-2026-3419 / GHSA-573f-x89g-hqp9

More information

Details

Description

Fastify incorrectly accepts malformed Content-Type headers containing trailing characters after the subtype token, in violation of RFC 9110 §8.3.1. For example, a request sent with Content-Type: application/json garbage passes validation and is processed normally, rather than being rejected with 415 Unsupported Media Type.

When regex-based content-type parsers are in use (a documented Fastify feature), the malformed value is matched against registered parsers using the full string including the trailing garbage. This means a request with an invalid content-type may be routed to and processed by a parser it should never have reached.

Impact

An attacker can send requests with RFC-invalid Content-Type headers that bypass validity checks, reach content-type parser matching, and be processed by the server. Requests that should be rejected at the validation stage are instead handled as if the content-type were valid.

Workarounds

Deploy a WAF rule to protect against this

Fix

The fix is available starting with v5.8.1.

Severity

  • CVSS Score: 5.3 / 10 (Medium)
  • Vector String: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:N

References

This data is provided by the GitHub Advisory Database (CC-BY 4.0).

fastify: request.protocol and request.host Spoofable via X-Forwarded-Proto/Host from Untrusted Connections

CVE-2026-3635 / GHSA-444r-cwp2-x5xf

More information

Details

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.

Severity

  • CVSS Score: 6.1 / 10 (Medium)
  • Vector String: CVSS:3.1/AV:A/AC:H/PR:N/UI:N/S:C/C:H/I:N/A:N

References

This data is provided by the GitHub Advisory Database (CC-BY 4.0).

Fastify has a Body Schema Validation Bypass via Leading Space in Content-Type Header

CVE-2026-33806 / GHSA-247c-9743-5963

More information

Details

Summary

A validation bypass vulnerability exists in Fastify v5.x where request body validation schemas specified via schema.body.content can be completely circumvented by prepending a single space character (\x20) to the Content-Type header. The body is still parsed correctly as JSON (or any other content type), but schema validation is entirely skipped.
This is a regression introduced by commit f3d2bcb (fix for CVE-2025-32442).

Details

The vulnerability is a parser-validator differential between two independent code paths that process the raw Content-Type header differently.
Parser path (lib/content-type.js, line ~67) applies trimStart() before processing:

const type = headerValue.slice(0, sepIdx).trimStart().toLowerCase()
// ' application/json' → trimStart() → 'application/json' → body is parsed ✓

Validator path (lib/validation.js, line 272) splits on /[ ;]/ before trimming:

function getEssenceMediaType(header) {
  if (!header) return ''
  return header.split(/[ ;]/, 1)[0].trim().toLowerCase()
}
// ' application/json'.split(/[ ;]/, 1) → ['']  (splits on the leading space!)
// ''.trim() → ''
// context[bodySchema][''] → undefined → NO validator found → validation skipped!

The ContentType class applies trimStart() before processing, so the parser correctly identifies application/json and parses the body. However, getEssenceMediaType splits on /[ ;]/ before trimming, so the leading space becomes a split point, producing an empty string. The validator looks up a schema for content-type "", finds nothing, and skips validation entirely.
Regression source: Commit f3d2bcb (April 18, 2025) changed the split delimiter from ';' to /[ ;]/ to fix CVE-2025-32442. The old code (header.split(';', 1)[0].trim()) was not vulnerable to this vector because .trim() would correctly handle the leading space. The new regex-based split introduced the regression.

PoC
const fastify = require('fastify')({ logger: false });

fastify.post('/transfer', {
  schema: {
    body: {
      content: {
        'application/json': {
          schema: {
            type: 'object',
            required: ['amount', 'recipient'],
            properties: {
              amount: { type: 'number', maximum: 1000 },
              recipient: { type: 'string', maxLength: 50 },
              admin: { type: 'boolean', enum: [false] }
            },
            additionalProperties: false
          }
        }
      }
    }
  }
}, async (request) => {
  return { processed: true, data: request.body };
});

(async () => {
  await fastify.ready();

  // BLOCKED — normal request with invalid payload
  const res1 = await fastify.inject({
    method: 'POST',
    url: '/transfer',
    headers: { 'content-type': 'application/json' },
    payload: JSON.stringify({ amount: 9999, recipient: 'EVIL', admin: true })
  });
  console.log('Normal:', res1.statusCode);
  // → 400 FST_ERR_VALIDATION

  // BYPASS — single leading space
  const res2 = await fastify.inject({
    method: 'POST',
    url: '/transfer',
    headers: { 'content-type': ' application/json' },
    payload: JSON.stringify({ amount: 9999, recipient: 'EVIL', admin: true })
  });
  console.log('Leading space:', res2.statusCode);
  // → 200 (validation bypassed!)
  console.log('Body:', res2.body);

  await fastify.close();
})();

Output:

Normal: 400
Leading space: 200
Body: {"processed":true,"data":{"amount":9999,"recipient":"EVIL","admin":true}}
Impact

Any Fastify application that relies on schema.body.content (per-content-type body validation) to enforce data integrity or security constraints is affected. An attacker can bypass all body validation by adding a single space before the Content-Type value. The attack requires no authentication and has zero complexity — it is a single-character modification to an HTTP header.
This vulnerability is distinct from all previously patched content-type bypasses:

CVE Vector Patched in 5.8.4?
CVE-2025-32442 Casing / semicolon whitespace ✅ Yes
CVE-2026-25223 Tab character (\t) ✅ Yes
CVE-2026-3419 Trailing garbage after subtype ✅ Yes
This finding Leading space (\x20) ❌ No

Recommended fix — add trimStart() before the split in getEssenceMediaType:

function getEssenceMediaType(header) {
  if (!header) return ''
  return header.trimStart().split(/[ ;]/, 1)[0].trim().toLowerCase()
}

Severity

  • CVSS Score: 7.5 / 10 (High)
  • Vector String: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N

References

This data is provided by the GitHub Advisory Database (CC-BY 4.0).

Release Notes

fastify/fastify (fastify)

v5.8.5

Compare Source

⚠️ Security Release

This fixes CVE CVE-2026-33806 GHSA-247c-9743-5963.

What's Changed
New Contributors

Full Changelog: fastify/fastify@v5.8.4...v5.8.5

v5.8.4

Compare Source

Full Changelog: fastify/fastify@v5.8.3...v5.8.4

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

Compare Source

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

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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 763427e to e343ccf Compare March 13, 2026 13:27
@renovate renovate Bot changed the title chore(deps): update dependency fastify to v5.8.1 [security] chore(deps): update dependency fastify to v5.8.3 [security] Mar 25, 2026
@renovate renovate Bot force-pushed the renovate/npm-fastify-vulnerability branch from e343ccf to 2b420e0 Compare March 25, 2026 20:45
@renovate renovate Bot changed the title chore(deps): update dependency fastify to v5.8.3 [security] chore(deps): update dependency fastify to v5.8.3 [security] - autoclosed Mar 27, 2026
@renovate renovate Bot closed this Mar 27, 2026
@renovate renovate Bot deleted the renovate/npm-fastify-vulnerability branch March 27, 2026 00:43
@renovate renovate Bot changed the title chore(deps): update dependency fastify to v5.8.3 [security] - autoclosed chore(deps): update dependency fastify to v5.8.3 [security] Mar 30, 2026
@renovate renovate Bot reopened this Mar 30, 2026
@renovate renovate Bot force-pushed the renovate/npm-fastify-vulnerability branch 2 times, most recently from 2b420e0 to dc36bfc Compare March 30, 2026 21:02
@renovate renovate Bot force-pushed the renovate/npm-fastify-vulnerability branch from dc36bfc to e3c0cee Compare April 16, 2026 10:09
@renovate renovate Bot changed the title chore(deps): update dependency fastify to v5.8.3 [security] chore(deps): update dependency fastify to v5.8.5 [security] Apr 16, 2026
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