CVE-2026-4786
python: cpython: Python: Arbitrary code execution via command injection in webbrowser.open() API
Severity
ImportantRed Hat Product Security
CVSS 3.1
Review impact separately from score.
Published · April 14, 2026
Updated · October 16, 2026
Description
A flaw was found in the Python webbrowser.open() API. If a specially crafted URL containing "%action" is processed, an attacker could bypass a previous mitigation for CVE-2026-4519. This bypass allows for command injection into the underlying shell, potentially leading to arbitrary code execution.
Statement
This flaw in the Python webbrowser.open() API allows for command injection and arbitrary code execution when processing specially crafted URLs containing "%action". This bypasses a previous mitigation for CVE-2026-4519.
CVSS score applicability
The CVSS score(s) listed for this vulnerability do not reflect the associated product's status, and are included for informational purposes to better understand the severity of this vulnerability.
Mitigation
Mitigation for this issue is either not available or the currently available options do not meet the Red Hat Product Security criteria comprising ease of use and deployment, applicability to widespread installation base, or stability.
CVSS / CWE
CVSS 3.1 · 7.1CVSS:3.1/AV:N/AC:H/PR:N/UI:R/S:U/C:H/I:H/A:L
CWE-88 · Improper Neutralization of Argument Delimiters in a Command ('Argument Injection')