CVE-2026-16117 json
@fastify/http-proxy vulnerable to prefix escape via URL-encoded characters
published 3mo ago modified 3mo ago also EUVD-2026-45379
- cvss
- 10.0
- version 3.1, CNA
- cisa kev
- Not listed
- not in CISA's catalog
- epss
- 0.4%
- EPSS 0.4% chance of exploitation in 30 days, percentile 38%
- public exploits
- 0
- none known
Summary
Impact: @fastify/http-proxy versions up to and including 11.5.0 fail to rewrite the request prefix when the prefix segment is URL-encoded. Fastify's router URL-decodes paths for route matching, but request.url retains the original encoded form, and the prefix-rewrite step uses a literal string replace against the decoded prefix. A request that encodes one or more characters of the configured prefix therefore matches the route but skips the rewrite, so the raw encoded path is forwarded to the upstream unchanged. The upstream then decodes the path and serves it, letting an attacker reach upstream paths that the proxy was configured to hide via rewritePrefix, including internal or administrative endpoints.
Patches: upgrade to @fastify/http-proxy 11.6.0.
Workarounds: none.
Patch / fix
- @fastify/http-proxy @fastify/http-proxy 11.6.0
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Check with FencerCISA SSVC
- Exploitation
- none
- Automatable
- yes
- Technical impact
- total
- Assessed
- 3mo ago
Exploit prediction
0.44% chance of exploitation in the next 30 days, higher than 38% of all scored CVEs (FIRST EPSS, 2026-11-09).
CVSS scores
| assigned by | version | score | vector |
|---|---|---|---|
| CNA | 3.1 | 10.0 | CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:H/I:H/A:N |
Affected products
- @fastify/http-proxy @fastify/http-proxy
Classification
- Weakness
-
- CWE-20 Improper Input Validation
References
-
github.com
/fastify/fastify-http-proxy/security/advisories/GHSA-mx7v-qhg9-2mvv
vendor-advisory
-
cna.openjsf.org
/security-advisories.html
vendor-advisory
Sources
- CVE List CVE-2026-16117
- NVD CVE-2026-16117
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