Edited-message disclosure via incomplete history filtering
Published May 12, 2026 · Updated May 12, 2026
Improper access control in Zulip before 12.0 allows remote authenticated users to read edited-away message text through the history API. get_message_edit_history passes raw entries to visible_edit_history_for_message, whose moves-policy branch removes only prev_content on move entries while retaining content, rendered_content, and the initial history entry. Exploitation requires the realm's moves-only policy and access to the target message; the result is disclosure of text that another user removed.
Summary
What happened
Improper access control in Zulip before 12.0 allows remote authenticated users to read edited-away message text through the history API. get_message_edit_history passes raw entries to visible_edit_history_for_message, whose moves-policy branch removes only prev_content on move entries while retaining content, rendered_content, and the initial history entry. Exploitation requires the realm's moves-only policy and access to the target message; the result is disclosure of text that another user removed.
The record
- CVE
- CVE-2026-40300
- Published
- May 12, 2026
- Updated
- May 12, 2026
- Vendor
- Zulip
- Product
- Zulip
- Classifications
- CWE-284, T1213
- Attack vector
- network
- Privileges
- authenticated
Timeline
How it unfolded
- May 12, 2026CVE publishedPublication date reported by the CVE source.
- May 12, 2026Record updatedLatest update available in the CVE record.
Exploitability
Present is not the same as exploitable
Compare your product and version with the public record. A matching version still requires validation against your environment.
Is a vulnerable build present?
Compare these published version ranges with your installed build and any vendor patches.
- Affected versionversion=< 12.0
What conditions does exploitation require?
What is affected?
Attacks
What attackers are doing with it
Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.
Public exploit references
- GHSA-jp8f-mvv6-89cr proof of conceptproof of concept · demonstrated
Labels summarize the accepted research assessment. They do not indicate a test against your environment.
Technologies
Your stack
See the directory against your own environment.
Your stack
Check the software in your environment
Book a demo to see how Hinoki identifies affected software and validates exploitability in your environment.
Book a demo