Vulnerability · Published Mar 20, 2026 · Assigned by GitHub_M
CVE-2026-33054Mesop: Path Traversal utilizing `FileStateSessionBackend` leads to Application Denial of Service and File Write/Deletion
Critical 10.0
In plain English
A critical-severity path traversal in mesop from mesop-dev. Proof-of-concept exploit code is public. The chance it is exploited in the next 30 days is estimated at 0.7% (higher than 55% of all known vulnerabilities). Fixed versions are available - upgrade the affected package.
Official description
Mesop is a Python-based UI framework that allows users to build web applications. Versions 1.2.2 and below contain a Path Traversal vulnerability that allows any user supplying an untrusted state_token through the UI stream payload to arbitrarily target files on the disk under the standard file-based runtime backend. This can result in application denial of service (via crash loops when reading non-msgpack target files as configurations), or arbitrary file manipulation. This vulnerability heavily exposes systems hosted utilizing FileStateSessionBackend. Unauthorized malicious actors could interact with arbitrary payloads overwriting or explicitly removing underlying service resources natively outside the application bounds. This issue has been fixed in version 1.2.3.
Affected packages & fixed versions
| Ecosystem | Package | Fixed in | Advisory |
|---|---|---|---|
| PyPI | mesop | 1.2.3 | GHSA-8qvf-mr4w-9x2c |
| PyPI | mesop | 1.2.3 | PYSEC-2026-411 |
Affected products (as reported)
Weakness: CWE-22 · Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:H/I:H/A:H
References
- https://github.com/mesop-dev/mesop/security/advisories/GHSA-8qvf-mr4w-9x2c x_refsource_CONFIRM
- https://github.com/mesop-dev/mesop/commit/c6b382f363b73ac32c402a2db3aadc7784f66a5b x_refsource_MISC
- https://github.com/mesop-dev/mesop/releases/tag/v1.2.3 x_refsource_MISC