Detection Guidance

This vulnerability can be detected by monitoring for requests that include suspicious or malicious values for the lng or ns parameters, such as path traversal sequences (e.g., ../../) or unusually long strings.

One way to detect exploitation attempts is to inspect HTTP request logs for query strings, cookies, or headers that set lng or ns to values containing path traversal patterns.

For example, you can use command-line tools like grep to search web server logs for such patterns.

• grep -E '\?lng=\.\./|\?ns=\.\./' /path/to/access.log
• grep -E 'lng=\.\./|ns=\.\./' /path/to/access.log

Additionally, monitoring for unexpected file read or write operations outside the intended locale directory on the filesystem may help detect exploitation.

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Executive Summary

The vulnerability exists in i18next-fs-backend versions prior to 2.6.4, which is a backend layer for i18next used in Node.js and Deno to load translation files from the filesystem.

The issue arises because the lng (language) and ns (namespace) options are directly substituted into file path templates without encoding or validation.

An attacker who can control these values can craft them to include path traversal sequences (like ".."), path separators, control characters, prototype keys, or very long strings.

This allows the attacker to read or overwrite files outside the intended locale directory by manipulating the file paths used by the backend.

For example, if lng is set to a path like "../../../../etc/passwd", the backend will attempt to read that file, potentially exposing sensitive system files.

This vulnerability has been fixed in version 2.6.4.

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Impact Analysis

This vulnerability can allow an attacker to read sensitive files on the server or overwrite files outside the intended translation directories.

If an attacker can influence the lng or ns parameters (for example, via HTTP requests where language is user-controlled), they could access sensitive system files such as password files or configuration files.

This could lead to information disclosure, unauthorized data access, or potentially modifying files leading to further compromise.

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Mitigation Strategies

To mitigate this vulnerability, upgrade i18next-fs-backend to version 2.6.4 or later, where the issue has been patched.

Additionally, avoid using untrusted input for the lng and ns options, especially when these values can be influenced by end users via query strings, cookies, or headers.

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Compliance Impact

The vulnerability allows attackers to read or overwrite arbitrary files on the filesystem by exploiting unsanitized input used in file path templates. This unauthorized access to sensitive files can lead to exposure or modification of personal or protected data.

Such unauthorized access and potential data breaches can negatively impact compliance with common standards and regulations like GDPR and HIPAA, which require strict controls over personal and sensitive data to prevent unauthorized disclosure or alteration.

Therefore, if exploited, this vulnerability could result in violations of data protection requirements, leading to legal and regulatory consequences.

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