CVE-2026-4786 HIGH

CVE-2026-4786: Incomplete mitigation of CVE-2026-4519, %action expansion for command injection to webbrowser.open()

Vendor Python Software Foundation
Product CPython
Weakness CWE-77
Published April 13, 2026
Last update June 30, 2026
View on NVD All CVEs

CVSS base score

7.0/10
Attack vector Local
Attack complexity Low
Privileges required None
User interaction —
Confidentiality —
Integrity —

CVSS vector

CVSS:4.0/AV:L/AC:L/AT:P/PR:N/UI:A/VC:H/VI:H/VA:N/SC:N/SI:N/SA:N

What the vulnerability does

01Description

Mitgation of CVE-2026-4519 was incomplete. If the URL contained "%action" the mitigation could be bypassed for certain browser types the "webbrowser.open()" API could have commands injected into the underlying shell. See CVE-2026-4519 for details.

Key dates

02Disclosure timeline

April 13, 2026 CVE published
June 30, 2026 Record updated