CVE-2026-33057: Mesop Affected by Unauthenticated Remote Code Execution via Test Suite Route /exec-py

Should you act?

Critical and remotely reachable

No known exploitation yet, but it is network-reachable without credentials. This signal is computed from CISA KEV, EPSS and CVSS data; it is not an editorial verdict.

• Not in CISA KEV, but CISA’s SSVC assessment records a public proof-of-concept, so attack code exists.
• EPSS 4.1%, percentile 91: FIRST’s model estimates a 4.1% chance of exploitation activity in the next 30 days, higher than 91% of all scored CVEs (elevated). EPSS is a probability, not a verdict.
• Remotely reachable with no login and no user interaction. If the vulnerable service is exposed to the internet, prioritize it.
• Only applies if your dependency tree includes mesop (PyPI) <= 1.2.2, fixed in 1.2.3. Check your lockfile, including transitive dependencies.

What it is

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/wsgiapp.py. The /exec-py route accepts base64 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 executemodule(modulepath...). This issue has been fixed in version 1.2.3.

From the GitHub advisory

Summary 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.

Details The AI codebase package includes a lightweight debugging Flask server inside ai/sandbox/wsgiapp.py. The /exec-py route accepts base64 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 executemodule(modulepath...).

PoC

Impact This presents trivial severity for systems publicly exposed or lacking strictly verified boundary firewalls due to absolute unauthenticated command injection privileges targeting the direct execution interpreter running this service sandbox.

Weakness type: CWE-94.

Product: mesop (PyPI) · Assigned by: GitHub_M · Published: 2026-03-20

Affected and fixed versions

Severity scores

• Attack vector: network (remotely reachable)
• Attack complexity: low
• Privileges required: none (no login)
• User interaction: none
• Scope: unchanged

CVSS measures how bad a flaw is if exploited, not how likely exploitation is. Read it next to the exploitation data below.

Exploitation and urgency

• CISA KEV: not listed (no confirmed in-the-wild exploitation known to CISA).
• CISA SSVC assessment: exploitation poc, automatable yes, technical impact total.
• FIRST EPSS (model of 2026-10-21): 4.11% probability of exploitation activity in the next 30 days; percentile 91.

Timeline

• 2026-03-18 — GitHub-reviewed advisory GHSA-gjgx-rvqr-6w6v published (critical)
• 2026-03-20 — CVE record published by GitHub_M
• 2026-03-25 — CVE record last updated

Sources and references

Original sources first. Version and fix details should always be confirmed against the vendor or project advisory.

Vulnerability records

1. GitHub Advisory GHSA-gjgx-rvqr-6w6v github.com
2. CVE.org record CVE-2026-33057 cve.org
3. NVD entry CVE-2026-33057 nvd.nist.gov

Other references from the CVE record and advisory

1. github.com github.com
2. github.com github.com

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