Vulnerability · Published Apr 3, 2026 · Assigned by GitHub_M

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

High 7.5

In plain English

A high-severity out-of-bounds read in mesop from mesop-dev. Proof-of-concept exploit code is public. The chance it is exploited in the next 30 days is estimated at 0.8% (higher than 55% of all known vulnerabilities). Fixed versions are available - upgrade the affected package.

Severity (CVSS 3.1)7.5High

Exploit odds (30 days)0.8%top 44.9% of all CVEs

Exploited in the wildNo reportsCISA SSVC: poc

Attack toolingNoneno public tooling known

Official 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.

Affected packages & fixed versions

Ecosystem	Package	Fixed in	Advisory
PyPI	mesop	1.2.5	GHSA-3jr7-6hqp-x679
PyPI	mesop	1.2.5	PYSEC-2026-2204

Affected products (as reported)

Vendor	Product	Versions
mesop-dev	mesop	>= 1.2.3, < 1.2.5

Weakness: CWE-125 · Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

References

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