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

> An unauthenticated attacker can cause a Denial of Service in Mesop applications by sending rapid WebSocket messages that exhaust system threads.

- **Severity:** High 7.5 (`CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H`)
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** Yes
- **Published:** 3 Apr 2026
- **Updated:** 6 Apr 2026
- **Also known as:** GHSA-3jr7-6hqp-x679, PYSEC-2026-2204

## What is CVE-2026-34824?

CVE-2026-34824 is a high-severity denial of service vulnerability in mesop-dev mesop, published on 3 Apr 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.

### 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.

Weakness: CWE-770 (Allocation of Resources Without Limits or Throttling), CWE-125 (Out-of-bounds Read)

## Which versions are affected by CVE-2026-34824?

3 open source packages ship an affected version, including mesop. It affects 1 product.


| Package | Ecosystem | Affected | Fixed in |
| --- | --- | --- | --- |
| `mesop` | PyPI | From 1.2.3 | 1.2.5 |
| `mesop` | PyPI | From 1.2.3 | 1.2.5 |
| `mesop` | PyPI | From 1.2.3 | 1.2.5 |

Products: Mesop-Dev Mesop.

## How do I fix CVE-2026-34824?

Upgrade mesop to 1.2.5 or later.

## Is CVE-2026-34824 being exploited?

It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-34824 exists.

## Other vulnerabilities in mesop-dev mesop

- [CVE-2026-33054](https://insights.sbomify.com/CVE-2026-33054/): Mesop has a Path Traversal utilizing `FileStateSessionBackend` leads to Application Denial of Service and File Write/Deletion (critical 10.0)
- [CVE-2026-33057](https://insights.sbomify.com/CVE-2026-33057/): Mesop Affected by Unauthenticated Remote Code Execution via Test Suite Route /exec-py (critical 9.8)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-34824 and fix it if it is affected.

What it is: CVE-2026-34824 is a high-severity denial of service vulnerability in mesop-dev mesop, published on 3 Apr 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.
Exploitation: It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-34824 exists.

Affected packages and fixed versions:
- mesop (PyPI): affected from 1.2.3; fixed in 1.2.5
- mesop (PyPI): affected from 1.2.3; fixed in 1.2.5
- mesop (PyPI): affected from 1.2.3; fixed in 1.2.5

Task:
1. Search the dependency manifests and lockfiles (for example package.json, package-lock.json, requirements.txt, poetry.lock, uv.lock, pom.xml, build.gradle, go.mod, Cargo.lock, Gemfile.lock) and any Dockerfiles for the affected packages, including transitive dependencies.
2. If an affected version is in use, upgrade it to the fixed version for its release line with the project's package manager, so the lockfile is regenerated. Prefer the smallest upgrade that fixes it.
3. If there is no fix, or the upgrade would break the build, do not guess: explain the risk and the safest workaround instead.
4. Run the tests and summarise what changed and why.
5. If nothing in the project is affected, say so and change nothing.

Reference: https://insights.sbomify.com/CVE-2026-34824/ (Markdown: https://insights.sbomify.com/CVE-2026-34824/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-34824
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-34824
- OSV: https://osv.dev/vulnerability/CVE-2026-34824

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-34824/
Summaries are generated and may contain mistakes; the official description above is the record.