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Vulnerability · Published Sep 23, 2026 · Assigned by GitHub_M

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

Medium 5.3

In plain English

A medium-severity security flaw in mesop from mesop-dev. There are no confirmed reports of exploitation so far. The chance it is exploited in the next 30 days is estimated at 0.5% (higher than 45% of all known vulnerabilities). Fixed versions are available - upgrade the affected package.

Severity (CVSS 4.0)5.3Medium
Exploit odds (30 days)0.5%top 55.1% of all CVEs
Exploited in the wildNo reportsCISA SSVC: none
Attack toolingNoneno public tooling known

Official 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.

Affected packages & fixed versions

EcosystemPackageFixed inAdvisory
PyPImesop1.3.4GHSA-g7f6-rxc4-qhph
PyPImesop1.3.4PYSEC-2026-4105

Affected products (as reported)

VendorProductVersions
mesop-dev mesop < 1.3.4

Weakness: CWE-117, CWE-150 · 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

References