CVE-2025-30358: Mesop Class Pollution Vulnerability Leading to DoS and Jailbreak Attacks
Summary
CVE-2025-30358: Mesop Class Pollution vulnerability leads to DoS and Jailbreak attacks. Affects mesop versions < 0.14.1. Fixed in 0.14.1. How to fix ↓
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Background
Mesop is an open-source application designed for managing and facilitating interactions with large language models (LLMs). It allows users to create and manage conversational agents, providing a framework for integrating various functionalities. However, the application is susceptible to a class pollution vulnerability that can compromise its security and functionality.
Vulnerability Detail
The identified vulnerability in Mesop (versions <= 0.14.0) allows attackers to overwrite global variables and class attributes during runtime. This class pollution can lead to denial of service (DoS) attacks, where the server becomes unresponsive. Additionally, it poses risks of identity confusion, enabling attackers to impersonate system roles within conversations. Such impersonation can facilitate jailbreak attacks when interacting with LLMs. The vulnerability is akin to JavaScript's prototype pollution, allowing manipulation of data-flow and control-flow, potentially leading to remote code execution (RCE) if exploitable gadgets are present.
How To Fix
Latest published version: 1.3.7 as of 23 Oct 2026
pip install --upgrade "mesop==1.3.7"Upgrading to it may include breaking changes; the version below is the minimum fixed release for this vulnerability.
If you need the minimum change
0.14.1
This is the first release that contains the fix.
pip install --upgrade "mesop==0.14.1"Tip — Not sure which version your app runs? Vulert can match this fix to it. Scan free →
Workaround
As a temporary workaround, users can limit the exposure of sensitive global variables and class attributes within their Mesop application. Implementing strict input validation and sanitization can also help mitigate the risk of exploitation until the package is updated.
Conclusion
The Mesop class pollution vulnerability (CVE-2025-30358) poses significant risks, including denial of service and potential exploitation through impersonation. Users are strongly advised to update to version 0.14.1 or later to mitigate these risks. Additionally, implementing workarounds can provide temporary relief until the update is applied.
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FAQ
The CVSS score of this vulnerability is 8.1, indicating a high severity level.
You can use Vulert's playground at Vulert Scanner to check if your application is affected by this vulnerability without requiring any signup.
The potential consequences include denial of service (DoS) attacks, identity confusion, and the possibility of jailbreak attacks when interacting with large language models.
Yes, a patch is available in version 0.14.1 of the Mesop package. Users should update to this version to mitigate the vulnerability.
Class pollution refers to the ability of an attacker to overwrite class attributes or global variables, which can lead to unintended behavior in the application, including security breaches and system instability.
References
Related vulnerabilities
Recent vulnerabilities recorded for mesop.
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