CVE-2026-84425 Details

A denial-of-service vulnerability exists in zhayujie CowAgent versions up to 2.1.3, specifically within the Browser Tool component. The issue arises in the function BrowserTool, located in the file agent/tools/browser/browser_tool.py. The vulnerability can be exploited remotely by manipulating the tool's 'wait' or 'evaluate' arguments, causing the application to occupy a shared browser thread and disrupt normal operations. This exploitation takes advantage of the tool's process-wide shared BrowserService, which serializes Playwright tasks through a single browser worker thread. When a long 'wait' or script execution is requested, the initial call can time out while the Playwright operation continues, blocking subsequent browser tasks from completing within the expected time frame.

To address this vulnerability, it is recommended to implement strict maximum timeout limits for browser 'wait' operations on the server side. Additionally, arbitrary browser 'evaluate' commands should be disabled by default or subjected to strict script deadlines and capability policies. Propagating cancellation from the caller to the BrowserService and its Playwright tasks can also help, as well as interrupting or recycling the browser context when a timeout occurs. Replacing the unbounded shared task queue with bounded, per-session queues and fair scheduling, along with establishing per-user or session limits for browser operations, can further mitigate the issue. Finally, adding regression tests to ensure that a timed-out browser task does not block subsequent browser probes can help prevent future occurrences of this problem.