critical CVSS 9.8

CVE-2026-33057·Python vulnerability

Mesop is a Python-based UI framework that allows users to build web applications. In versions 1.2.2 and below, an explicit web endpoint inside the ai/ testing module infrastructure directly ingests untrusted Python code strings unconditionally without authentication measures, yielding standard Unrestricted Remote Code Execution. Any individual capable of routing HTTP logic to this server block will gain explicit host-machine command rights. The AI codebase package includes a lightweight debugging Flask server inside ai/sandbox/wsgi_app.py. The /exec-py route accepts base_64 encoded raw string payloads inside the code parameter natively evaluated by a basic POST web request. It saves it rapidly to the operating system logic path and injects it recursively using execute_module(module_path...). This issue has been fixed in version 1.2.3.

Severity
critical
Software
Python
Fixed in
1.2.3
Published
2026-03-20

Affected versions

Until: 1.2.3

Fixed in: 1.2.3

How to fix this CVE

Upgrade Python and the Mesop framework to version 1.2.3 or later to eliminate an unauthenticated remote code execution vulnerability in the debugging endpoint. Organizations running Mesop versions 1.2.2 and earlier should prioritize this patch immediately, as the flaw allows attackers to execute arbitrary Python code on the host system without authentication.

sudo dnf update python3 && pip3 install --upgrade mesop>=1.2.3

Defensia detects this vulnerability

What an exploitation attempt looks like

Sample log line indicative of exploitation attempts:

POST /exec-py HTTP/1.1.*code=([A-Za-z0-9+/=]+)

WAF mitigation (if patching is not yet possible)

Add this rule to your WAF to block exploitation attempts while you schedule the patch. 

Block or require authentication for all POST requests to /exec-py endpoint; implement IP whitelisting for the debug server; disable the ai/sandbox/wsgi_app.py debugging server in production environments; enforce TLS/SSL for all Mesop framework endpoints.

How to check if you are affected

  1. Check installed Mesop version: pip3 show mesop | grep Version
  2. Identify if the ai/sandbox/wsgi_app.py debug server is running: netstat -tuln | grep -E ':(5000|8080|8000)' and ps aux | grep wsgi_app.py
  3. Search application logs for POST requests to /exec-py endpoint: grep -r '/exec-py' /var/log/ or check web server access logs for base64-encoded 'code' parameters
  4. Verify the patch by confirming Mesop version is 1.2.3 or higher: pip3 show mesop | grep 'Version: 1.2.3' and test that the /exec-py endpoint is disabled or requires authentication

FAQ

What is CVE-2026-33057?

CVE-2026-33057 is a critical remote code execution flaw in Mesop's debugging Flask server that exposes an unauthenticated /exec-py endpoint accepting base64-encoded Python code, allowing attackers to execute arbitrary commands on the host machine without any credentials.

Is CVE-2026-33057 being actively exploited?

According to CISA's Known Exploited Vulnerabilities catalog, CVE-2026-33057 is not currently being actively exploited in the wild, and no public exploit code is available.

What versions of Python are affected by CVE-2026-33057?

CVE-2026-33057 affects Mesop versions up to and including 1.2.2; the vulnerability is patched in version 1.2.3 and later. The issue resides in the Mesop framework itself rather than core Python versions.

How do I check if my server is vulnerable to CVE-2026-33057?

Run 'pip3 show mesop' to check the installed version; if it is 1.2.2 or lower, your system is vulnerable. Additionally, verify if the debug server is exposed by testing curl -X POST http://localhost:5000/exec-py -d 'code=base64_string' from a remote network.

Does Defensia detect CVE-2026-33057?

Yes — Defensia's CVE advisory scanner compares installed package versions against the NVD database. If Mesop is installed on a monitored server, CVE-2026-33057 will appear in your dashboard with remediation steps.

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References

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