Vulnerability-Lookup

FKIE_CVE-2026-16732

Vulnerability from fkie_nvd - Published: 2026-08-18 21:16 - Updated: 2026-09-02 14:39

Severity

6.1 (Medium) - CVSS:3.1/AV:A/AC:H/PR:N/UI:N/S:C/C:H/I:N/A:N

Summary

fastify is a fast and low overhead web framework for Node.js. Impact: the fix for CVE-2026-3635 added a guard on the forwarded-header reads used to derive the request host, protocol, hostname, ip, and ips values, checking the connecting address. That guard closes the IP, CIDR, and custom-function forms of trustProxy correctly, because those forms compile to predicates that inspect the connecting address. The hop-count form, where trustProxy is set to a number, compiles to a predicate that structurally ignores the address, so the guard is always satisfied for any hop count of one or more. Applications configured with a numeric trustProxy value, such as trustProxy set to 1 for a single reverse proxy, remain vulnerable: an attacker who can reach the Fastify origin directly, bypassing the front-facing proxy, can spoof the forwarded request fields exactly as in the unpatched version. The impact class matches the parent CVE-2026-3635, including host injection in generated URLs, HTTPS-enforcement bypass, secure-cookie and CSRF-origin bypass, and host-based routing and cache poisoning. Affected versions are fastify from 5.8.3 up to but not including 5.12.1. Patches: patched in fastify 5.12.1, where the numeric form of trustProxy is disabled at runtime and removed from the TypeScript type union. Workarounds: migrate to an IP, CIDR, or custom-function trustProxy value that validates the connecting address, and ensure the Fastify origin is only reachable through the trusted proxy chain.

References

	URL	Tags
	ce714d77-add3-4f53-aff5-83d477b104bb	https://cna.openjsf.org/security-advisories.html	Third Party Advisory
	ce714d77-add3-4f53-aff5-83d477b104bb	https://github.com/fastify/fastify/security/advisories/GHSA-3m5p-2c4r-xxw2	Mitigation, Vendor Advisory

Impacted products

	Vendor	Product	Version
	fastify	fastify	*

JSON

To clipboard

{
  "affected": [
    {
      "affectedData": [
        {
          "defaultStatus": "unaffected",
          "packageURL": "pkg:npm/fastify",
          "product": "fastify",
          "vendor": "fastify",
          "versions": [
            {
              "lessThan": "5.12.1",
              "status": "affected",
              "version": "5.8.3",
              "versionType": "semver"
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              "status": "unaffected",
              "version": "5.12.1",
              "versionType": "semver"
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              "matchCriteriaId": "DF5470B1-C71F-456B-BEE3-6235FA247692",
              "versionEndExcluding": "5.12.1",
              "versionStartIncluding": "5.8.3",
              "vulnerable": true
            }
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        }
      ]
    }
  ],
  "cveTags": [],
  "descriptions": [
    {
      "lang": "en",
      "value": "fastify is a fast and low overhead web framework for Node.js. Impact: the fix for CVE-2026-3635 added a guard on the forwarded-header reads used to derive the request host, protocol, hostname, ip, and ips values, checking the connecting address. That guard closes the IP, CIDR, and custom-function forms of trustProxy correctly, because those forms compile to predicates that inspect the connecting address. The hop-count form, where trustProxy is set to a number, compiles to a predicate that structurally ignores the address, so the guard is always satisfied for any hop count of one or more. Applications configured with a numeric trustProxy value, such as trustProxy set to 1 for a single reverse proxy, remain vulnerable: an attacker who can reach the Fastify origin directly, bypassing the front-facing proxy, can spoof the forwarded request fields exactly as in the unpatched version. The impact class matches the parent CVE-2026-3635, including host injection in generated URLs, HTTPS-enforcement bypass, secure-cookie and CSRF-origin bypass, and host-based routing and cache poisoning. Affected versions are fastify from 5.8.3 up to but not including 5.12.1. Patches: patched in fastify 5.12.1, where the numeric form of trustProxy is disabled at runtime and removed from the TypeScript type union. Workarounds: migrate to an IP, CIDR, or custom-function trustProxy value that validates the connecting address, and ensure the Fastify origin is only reachable through the trusted proxy chain."
    }
  ],
  "id": "CVE-2026-16732",
  "lastModified": "2026-09-02T14:39:20.050",
  "metrics": {
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          "attackVector": "ADJACENT_NETWORK",
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          "baseScore": 6.1,
          "baseSeverity": "MEDIUM",
          "confidentialityImpact": "HIGH",
          "integrityImpact": "NONE",
          "privilegesRequired": "NONE",
          "scope": "CHANGED",
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        "impactScore": 4.0,
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        "type": "Secondary"
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}

CVE-2026-16732 (GCVE-0-2026-16732)

Vulnerability from cvelistv5 – Published: 2026-08-18 20:30 – Updated: 2026-08-19 13:16

Title

fastify vulnerable to X-Forwarded-* spoofing under trustProxy hop-count

Summary

Severity

6.1 (Medium)


                        
                          CVSS:3.1/AV:A/AC:H/PR:N/UI:N/S:C/C:H/I:N/A:N

SSVC

Exploitation: none Automatable: no Technical Impact: partial

CISA Coordinator · CISA-ADP (v2.0.3)

Decision recorded 2026-08-19 13:15 UTC

CWE

CWE-348 - Use of Less Trusted Source

Assigner

openjs redhat root

References

2 references

URL	Tags
https://github.com/fastify/fastify/security/advis…
https://cna.openjsf.org/security-advisories.html

Impacted products

1 product

Vendor	Product	Version
fastify	fastify	Affected: 5.8.3 , < 5.12.1 (semver) Unaffected: 5.12.1 (semver)

Credits

alimony mcollina climba03003 UlisesGascon

Show details on NVD website

JSON

To clipboard

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                "timestamp": "2026-08-19T13:15:46.091425Z",
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Sightings

Author	Source	Type	Date	Other

Nomenclature

Seen: The vulnerability was mentioned, discussed, or observed by the user.
Confirmed: The vulnerability has been validated from an analyst's perspective.
Published Proof of Concept: A public proof of concept is available for this vulnerability.
Exploited: The vulnerability was observed as exploited by the user who reported the sighting.
Patched: The vulnerability was observed as successfully patched by the user who reported the sighting.
Not exploited: The vulnerability was not observed as exploited by the user who reported the sighting.
Not confirmed: The user expressed doubt about the validity of the vulnerability.
Not patched: The vulnerability was not observed as successfully patched by the user who reported the sighting.

Detection rules are retrieved from Rulezet.

The MITRE ATT&CK techniques below are AI-generated suggestions, inferred from the description of the vulnerability by the CIRCL/vulnerability-attack-technique-classification-roberta-base model, served locally by ML-Gateway. They have not been verified by an analyst and are provided for guidance only.
The approach is described in our paper Mapping CVEs to MITRE ATT&CK Techniques: A Curated Gold-Set Classifier and the Limits of LLM-Assisted Label Expansion.
Browse all ATT&CK techniques and the vulnerabilities related to each.

Related by attack behaviour

Vulnerabilities whose description is nearest to this one in the vector space of the CIRCL/vulnerability-attack-technique-biencoder model. This is a similarity search over the bi-encoder space (plain cosine), not a classification, and it has no measured accuracy.