CVE-2026-85124
@fastify/http-proxy vulnerable to prefix escape via backslash dot-segments
Description
@fastify/http-proxy versions before 11.6.2 do not validate proxied HTTP request paths for backslash based dot-segments before forwarding them to the configured upstream. The plain HTTP request handler skips the destination validation that the WebSocket path performs, and the underlying reply-from library only rejects forward-slash traversal, so a request containing backslash dot-segments can escape the boundary set by the prefix and rewritePrefix options. An unauthenticated network attacker can use this to reach upstream paths that were meant to stay hidden behind the proxy, resulting in disclosure of internal endpoints. This is a path traversal issue (CWE-22). Users should upgrade to @fastify/http-proxy 11.6.2 or later.
INFO
Published Date :
Sept. 3, 2026, 10:51 a.m.
Last Modified :
Sept. 3, 2026, 10:51 a.m.
Remotely Exploit :
Yes !
Source :
openjs
Affected Products
The following products are affected by CVE-2026-85124
vulnerability.
Even if cvefeed.io is aware of the exact versions of the
products
that
are
affected, the information is not represented in the table below.
No affected product recoded yet
CVSS Scores
| Score | Version | Severity | Vector | Exploitability Score | Impact Score | Source |
|---|---|---|---|---|---|---|
| CVSS 3.1 | HIGH | ce714d77-add3-4f53-aff5-83d477b104bb | ||||
| CVSS 3.1 | HIGH | MITRE-CVE |
Solution
- Upgrade @fastify/http-proxy to 11.6.2 or later.
- Validate proxied HTTP request paths.
- Ensure upstream paths are not exposed.
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CVE-2026-85124 vulnerability anywhere in the article.