CVE-2026-77357
HighCVSS 8.7Exploitation Probability (EPSS)
Low risk23th percentile - higher than 23% of all known CVEs
Summary
Mesop prior to version 1.3.3, when running in debug mode, exposes a GET /hot-reload endpoint whose unbounded loop depends on the user-supplied counter parameter. An unauthenticated attacker can send requests with high counter values, exhausting the worker pool and making the server unavailable. The attack requires minimal effort and leaves the server unresponsive until manually restarted.
Risk Assessment
A single attacker can cause complete unavailability of the Mesop server, disrupting web applications built with this framework.
Recommendation
Upgrade Mesop to version 1.3.3 or later, which includes a fix limiting the loop in the hot-reload endpoint.
Other vulnerabilities in Mesop
See all- CVE-2026-93421Medium
Mesop is a Python-based UI framework for building web applications. Prior to 1.3.4, the unauthenticated /__csp__ endpoint passes attacker-controlled document-uri, blocked-uri, and violated-directive values to the csp_report handler in mesop/server/static_file_serving.py, which prints them to standard output without neutralizing terminal control sequences. When an operator views the resulting logs in an ANSI-capable terminal, injected ANSI or VT100 sequences can clear or reposition the display, hide text, or present forged messages, reducing the integrity of monitoring and incident-response output. This issue is fixed in version 1.3.4.
- CVE-2026-34824High
Mesop, a Python-based UI framework, from version 1.2.3 to before version 1.2.5 contains an uncontrolled resource consumption vulnerability in the WebSocket implementation. An unauthenticated attacker can send a rapid succession of WebSocket messages, forcing the server to spawn an unbounded number of OS threads, leading to thread exhaustion and Out of Memory (OOM) errors, causing a complete Denial of Service (DoS).
Original NVD description (English source)
Mesop is a Python-based UI framework that allows users to build web applications. Prior to 1.3.3, applications running in debug mode expose a GET /hot-reload endpoint whose unbounded loop depends on the user-supplied counter parameter, allowing an unauthenticated attacker to hold worker threads with high counter values until the worker pool is exhausted and the server becomes unavailable. A single unauthenticated attacker can crash the Mesop server with minimal effort. Because the attack leverages worker exhaustion, the server remains unresponsive until it is manually restarted. This issue is fixed in version 1.3.3.
Vulnerability data from NVD (NIST) · CISA KEV · EPSS