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TI-2026-83779 Aliases CVE-2026-120213

Path escape in @fastify/http-proxy via decoded route parameters

Priority MEDIUM 48CWE-22Published · Updated

Key facts

Attack vector
Network
Privileges required
None
User interaction
None
Attack complexity
Low
Impact type
—
Confidentiality · integrity · availability
High · High · None
Fix status
Partial Red Hat: 2 without a fix

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

Summary

@fastify/http-proxy from 9.0.0 before 11.6.6 substitutes URL-decoded route parameters into rewritePrefix without re-encoding them when parameterized prefix and rewritePrefix options are used. A parameter value that encodes a path separator together with a query or fragment delimiter decodes into real separators and delimiters, which inject extra upstream path segments and strip the enforced suffix (CWE-22). An unauthenticated remote attacker can reach upstream locations outside the intended prefix, which may enable server-side request forgery or authorization bypass in the proxied service.

Written with Claude Haiku 5.5 from the sources below · 2026-11-06

Description from the CNA

@fastify/http-proxy is a Fastify plugin that proxies HTTP requests to an upstream server under a configured prefix. In versions 9.0.0 through 11.6.5, when an application uses parameterized prefix and rewritePrefix options to pin clients to a fixed upstream path, the plugin substitutes URL-decoded route parameters into rewritePrefix without re-encoding them. A parameter value that encodes a path separator together with a fragment or query delimiter therefore decodes into real separators and delimiters that inject extra upstream path segments and strip the mandatory suffix the rewritePrefix was meant to enforce, without using any dot-dot traversal. An unauthenticated remote attacker can use this to reach upstream locations outside the intended prefix, leading to path-restriction bypass and, depending on the upstream, server-side request forgery or authorization bypass in the proxied service. The issue is fixed in @fastify/http-proxy 11.6.6, and users should upgrade to 11.6.6 or later. There is no workaround other than upgrading.

Why it matters now

Exploitation None reported CISA SSVC · not in CISA KEV
EPSS 0.0069 53rd percentileScored 2026-11-07
Fix Partial @fastify/http-proxy (@fastify/http-proxy): 11.6.6Red Hat: 2 without a fix

SSVC decision points

CISA ADP · SSVC 2.0.3

Exploitation
None
Automatable
Yes
Technical impact
Total

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

Affected products

VendorProductAffected versionsFixed inStatusSource
fastify@fastify/http-proxy9.0.0 to before 11.6.611.6.6Patch availableCNA
  • @fastify/http-proxy Vendorfastify Affected 9.0.0 to before 11.6.6 Fixed in 11.6.6 Patch available CNA

CPE names Threatist (inferred) · 1

Inferred from how NVD named this product before; not given by a source.

CPEVersionsRoleVendor
cpe:2.3:a:fastify:fastify\/http-proxy:*:*:*:*:*:*:*:*——fastify
  • cpe:2.3:a:fastify:fastify\/http-proxy:*:*:*:*:*:*:*:* Versions — — ·fastify

Remediation

Upgrade @fastify/http-proxy to 11.6.6 or later, which fixes the flaw. Red Hat lists Red Hat OpenShift AI (RHOAI) and Red Hat OpenShift Dev Spaces as affected without a fix, with the plan none_available.

Written with Claude Haiku 5.5 from the sources below · 2026-11-06

  • Fix · CNA @fastify/http-proxy (@fastify/http-proxy) Fixed in 11.6.6

Vendor assessments

Red Hat

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

ProductStatusPlan or fix
Red Hat OpenShift AI (RHOAI)AffectedNo fix yet
Red Hat OpenShift Dev SpacesAffectedNo fix yet

Timeline

  1. 2026-11-02 Threatist record created from CVE-2026-120213
  2. 2026-11-02 CISA SSVC decision points changed
  3. 2026-11-06 Affected versions changed · Red Hat
  4. 2026-11-06 CVSS score added · Red Hat

References

Other 2

  • TI-2026-26180 @fastify/express vulnerable to middleware authentication bypass via URL normalization… CVSS 4.0CRITICAL 9.1
  • TI-2026-26179 @fastify/express vulnerable to middleware path doubling causing authentication bypass in child plugin scopes CVSS 3.1CRITICAL 9.1
  • TI-2026-26177 @fastify/reply-from vulnerable to connection header abuse enabling stripping of proxy-added headers CVSS 4.0CRITICAL 9.0
  • TI-2026-05498 @fastify/middie vulnerable to middleware authentication bypass in child plugin scopes CVSS 3.1CRITICAL 9.1
  • TI-2023-15307 Cross-site request forgery in npm @fastify/oauth2 CVSS 3.1HIGH 8.8
  • TI-2022-18664 Denial of service in Fastify via Content-Type header CVSS 3.1HIGH 7.5
See all 76 →

Sources

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