#VU127959 Improper access control in Zulip Server - CVE-2026-40300

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Main Vulnerability Database Vulnerabilities #VU127959

#VU127959 Improper access control in Zulip Server - CVE-2026-40300

Published: April 27, 2026


Vulnerability identifier: #VU127959
Vulnerability risk: Medium
CVSSv4.0: CVSS:4.0/AV:N/AC:L/AT:P/PR:L/UI:N/VC:H/VI:N/VA:N/SC:N/SI:N/SA:N/E:P/U:Green
CVE-ID: CVE-2026-40300
CWE-ID: CWE-284
Exploitation vector: Remote access
Exploit availability: Public exploit is available
Vulnerable software:
Zulip Server
Software vendor:
Zulip

Description

The vulnerability allows a remote attacker to gain unauthorized access to otherwise restricted functionality.

The vulnerability exists due to improper access restrictions in "moves only" policy within /api/v1/messages/{id}/history. A remote user can bypass implemented security restrictions and gain unauthorized access to message edit history.


Remediation

Install updates from vendor's website.

External links