SB2026042731 - Information disclosure in Zulip Server
Published: April 27, 2026
Security Bulletin ID
SB2026042731
CSH Severity
Medium
Patch available
YES
Number of vulnerabilities
1
Exploitation vector
Remote access
Highest impact
Information disclosure
Breakdown by Severity
- Low
- Medium
- High
- Critical
Description
This security bulletin contains information about 1 vulnerability.
1) Improper access control (CVE-ID: CVE-2026-40300)
CWE-ID: CWE-284 - Improper Access Control
CVSSv4: 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
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 update from vendor's website.