TI-2026-03135 Aliases CVE-2026-3635 GHSA-444r-cwp2-x5xf

Fastify request.protocol and request.host spoofable via X-Forwarded-Proto/Host from…

LOW 26CWE-348Published 2026-03-23 · Updated 2026-03-23

Key facts

Attack vector: Adjacent network
Privileges required: None
User interaction: None
Attack complexity: High
Impact type: —
Confidentiality · integrity · availability: High · None · None
Fix status: Partial Red Hat: 3 without a fix

Attack profile from CVSS 3.1 · CNA. Fix status from CNA, GitHub and Red Hat.

Summary

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.

Why it matters now

Exploitation None reported CISA SSVC · not in CISA KEV

EPSS 0.00161 5th percentileScored 2026-11-07

Fix Partial fastify (fastify): 5.8.3fastify (npm): 5.8.3Red Hat: 3 without a fix

SSVC decision points

CISA ADP · SSVC 2.0.3

Exploitation: None
Automatable: No
Technical impact: Partial

The decision (Track, Attend, Act) also depends on your mission and well-being impact; see CISA's SSVC guide.

Affected products

Vendor	Product	Affected versions	Fixed in	Status	Source
fastify	fastify	up to 5.8.2	5.8.3	Patch available	CNA
—	fastify (npm)	before 5.8.3	5.8.3	Patch available	GHSA-444r-cwp2-x5xf

fastify Vendorfastify Affected up to 5.8.2 Fixed in 5.8.3 Patch available CNA
fastify (npm) Vendor— Affected before 5.8.3 Fixed in 5.8.3 Patch available GHSA-444r-cwp2-x5xf

CPE configurations NVD · 1

CPE	Versions	Role	Vendor
cpe:2.3:a:fastify:fastify::::::node.js::*	before 5.8.3	Vulnerable	fastify

cpe:2.3:a:fastify:fastify:*:*:*:*:*:node.js:*:* Versions before 5.8.3 Vulnerable ·fastify

Remediation

Fix · CNA fastify (fastify) Fixed in 5.8.3
Fix · GHSA-444r-cwp2-x5xf fastify (npm) Fixed in 5.8.3 Advisory →

Vendor assessments

Red Hat

Red Hat rating: Moderate. Red Hat's page for this CVE →

Product	Status	Plan or fix
Red Hat Enterprise Linux AI (RHEL AI) 3	Affected	No fix yet: Fix deferred
Red Hat OpenShift AI (RHOAI)	Affected	No fix yet: Fix deferred
Red Hat OpenShift Dev Spaces	Affected	No fix yet: Fix deferred

Timeline

2026-10-02 Threatist record created from CVE-2026-3635
2026-10-03 Alias added: GHSA-444r-cwp2-x5xf

References

Advisory 4

Other 2

TI-2022-18664 Denial of service in Fastify via Content-Type header CVSS 3.1HIGH 7.5
TI-2025-23513 Fastify vulnerable to invalid content-type parsing, which could lead to validation bypass CVSS 3.1HIGH 7.5
TI-2026-58050 fastify vulnerable to request validation bypass via skipped boolean false schemas CVSS 3.1HIGH 7.5
TI-2026-58022 fastify vulnerable to header validation bypass via incomplete schema case normalization CVSS 3.1HIGH 7.5
TI-2026-53284 fastify vulnerable to authentication bypass via malformed URLs reaching encapsulated not-found handlers CVSS 3.1HIGH 7.5
TI-2026-26178 fastify vulnerable to Body Schema Validation Bypass via Leading Space in Content-Type Header CVSS 3.1HIGH 7.5

See all 15 →

Sources

This product uses the NVD API but is not endorsed or certified by the NVD. Sources and licences