CVE-2026-3635
- Source
- https://cve.org/CVERecord?id=CVE-2026-3635
- Import Source
- https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2026-3635.json
- JSON Data
- https://api.osv.dev/v1/vulns/CVE-2026-3635
- Aliases
- Downstream
- Published
- 2026-03-23T13:53:00.386Z
- Modified
- 2026-07-08T08:12:58.860149635Z
- Severity
-
- 6.1 (Medium) CVSS_V3 - CVSS:3.1/AV:A/AC:H/PR:N/UI:N/S:C/C:H/I:N/A:N CVSS Calculator
- Summary
- Fastify request.protocol and request.host spoofable via X-Forwarded-Proto/Host from untrusted connections when trustProxy uses restrictive trust function
- 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.
- Database specific
{ "osv_generated_from": "https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/3xxx/CVE-2026-3635.json", "cna_assigner": "openjs", "cwe_ids": [ "CWE-348" ] }- References
-
- https://www.cve.org/CVERecord?id=CVE-2026-3635
- https://cna.openjsf.org/security-advisories.html
- https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/3xxx/CVE-2026-3635.json
- https://github.com/fastify/fastify/security/advisories/GHSA-444r-cwp2-x5xf
- https://nvd.nist.gov/vuln/detail/CVE-2026-3635
Affected packages
Git / github.com/fastify/fastify
Affected ranges
- Type
- GIT
- Repo
- https://github.com/fastify/fastify
- Events
-
Introduced0 Unknown introduced commit / All previous commits are affectedFixed
- Database specific
{ "source": [ "AFFECTED_FIELD", "CPE_RANGE" ], "cpe": "cpe:2.3:a:fastify:fastify:*:*:*:*:*:node.js:*:*", "extracted_events": [ { "introduced": "0" }, { "last_affected": "5.8.2" }, { "fixed": "5.8.3" } ] }