Information Disclosure in CowAgent Browser Tool

Executive Summary

CVE-2026-15329 is a local file disclosure vulnerability in the CowAgent Browser Tool, affecting versions up to 2.1.0. The vulnerability occurs because the browser tool accepts attacker-controlled URLs, including file:// URLs, without validating or restricting the URL schemes. An authenticated user can exploit this by providing a file:// URL to the browser.navigate action, which causes the tool to open and read local files on the system. The contents of these files are then exfiltrated through the tool's snapshot response, effectively turning the browser feature into a local file reader.

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Compliance Impact

The vulnerability allows an authenticated attacker to read local files accessible by the CowAgent process, potentially exposing sensitive information such as configuration files, credentials, or logs.

This information disclosure could lead to non-compliance with data protection regulations like GDPR or HIPAA if personal or sensitive data is exposed without proper authorization.

Since the exploit enables unauthorized access to sensitive data, organizations using affected versions of CowAgent may face risks related to confidentiality and data privacy requirements mandated by these standards.

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Impact Analysis

This vulnerability can lead to the disclosure of sensitive local files that the CowAgent process user has access to, such as configuration files, credentials, or logs. An attacker with authenticated access to the browser tool can exploit this to read and exfiltrate sensitive information, potentially compromising the security and privacy of the system or application.

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Detection Guidance

This vulnerability can be detected by checking if the CowAgent Browser Tool allows navigation to attacker-controlled URLs, especially those using non-network schemes like file://, about:, or data:. Detection involves verifying if authenticated users can invoke the browser.navigate action with such URLs and receive local file contents in the snapshot response.

A practical detection method is to attempt to navigate the browser tool to a local file URI (e.g., file:///etc/passwd) and observe if the file contents are returned in the snapshot response.

Since the vulnerability involves the browser_tool.py passing URLs directly to Playwright's page.goto() without validation, monitoring or logging calls to this function with suspicious URL schemes can also help detect exploitation attempts.

• Attempt to invoke the browser.navigate action with a file:// URL and check if the response contains local file contents.
• Monitor logs or network traffic for browser.navigate requests containing non-network URL schemes.

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Mitigation Strategies

Immediate mitigation steps include restricting or disabling the browser.navigate action for authenticated users until a patch is available.

Implement input validation or filtering to enforce a scheme allowlist on URLs accepted by the Browser Tool, blocking non-network schemes such as file://, about:, and data:.

Limit access to the CowAgent Browser Tool to trusted users only, as exploitation requires authenticated access.

Monitor and audit usage of the browser.navigate action to detect any suspicious attempts to access local files.

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