CVE-2026-120214
Description
A flaw was found in @fastify/http-proxy. This vulnerability allows an unauthenticated remote attacker to cause information disclosure by bypassing intended proxy routing restrictions. Due to improper path validation that processes backslashes before decoding request paths, encoded backslashes and directory navigation sequences can pass uninspected. When requests are forwarded to an upstream server that treats backslashes as folder separators, attackers can retrieve sensitive resources outside the configured proxy directory.
Statement
A confidentiality-only information disclosure flaw exists in @fastify/http-proxy versions 11.6.0-11.6.2. The destination validation normalizes literal backslashes before percent-decoding the request path, so paths with encoded backslashes and dot-segments bypass the configured proxy prefix restriction; when the upstream service behind the proxy treats decoded backslash as a path separator (e.g., a Windows static-file host), the forwarded request reaches sibling locations outside the intended prefix. The issue is fixed in 11.6.3, and there is no workaround per the upstream GHSA advisory (GHSA-hr26-gmr2-pwcv).
Mitigation
Upgrade the bundled @fastify/http-proxy package to 11.6.3 or later. No upstream workaround is available per GHSA-hr26-gmr2-pwcv.
Common Vulnerability Scoring System (CVSS) Score Details
Info alert:Important note
CVSS scores for open source components depend on vendor-specific factors (e.g. version or build chain). Therefore, Red Hat's score and impact rating can be different from NVD and other vendors. Red Hat remains the authoritative CVE Naming Authority (CNA) source for its products and services (see Red Hat classifications).
The following CVSS metrics and score provided are preliminary and subject to review.
CVSS v3 Score Breakdown
| Red Hat | NVD | cve.org | |
|---|---|---|---|
| Base Score | 5.9 | N/A | 5.9 |
| Attack Vector | Network | N/A | Network |
| Attack Complexity | High | N/A | High |
| Privileges Required | None | N/A | None |
| User Interaction | None | N/A | None |
| Scope | Unchanged | N/A | Unchanged |
| Confidentiality | High | N/A | High |
| Integrity Impact | None | N/A | None |
| Availability Impact | None | N/A | None |
Vector
Red Hat: CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:N/A:N
cve.org: CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:N/A:N
Understanding the Weakness (CWE)
Integrity,Confidentiality,Availability
Technical Impact: Execute Unauthorized Code or Commands
The attacker may be able to create or overwrite critical files that are used to execute code, such as programs or libraries.
Integrity
Technical Impact: Modify Files or Directories
The attacker may be able to overwrite or create critical files, such as programs, libraries, or important data. If the targeted file is used for a security mechanism, then the attacker may be able to bypass that mechanism. For example, appending a new account at the end of a password file may allow an attacker to bypass authentication.
Confidentiality
Technical Impact: Read Files or Directories
The attacker may be able to read the contents of unexpected files and expose sensitive data. If the targeted file is used for a security mechanism, then the attacker may be able to bypass that mechanism. For example, by reading a password file, the attacker could conduct brute force password guessing attacks in order to break into an account on the system.
Availability
Technical Impact: DoS: Crash, Exit, or Restart
The attacker may be able to overwrite, delete, or corrupt unexpected critical files such as programs, libraries, or important data. This may prevent the product from working at all and in the case of protection mechanisms such as authentication, it has the potential to lock out product users.
Frequently Asked Questions
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