Vulnerability · Published May 12, 2026 · Assigned by GitHub_M

CVE-2026-40300Zulip: Message edit history visible in "moves only" policy through /api/v1/messages/{id}/history

Medium 6.0

In plain English

A medium-severity improper access control in zulip from zulip. There are no confirmed reports of exploitation so far. The chance it is exploited in the next 30 days is estimated at 0.2% (higher than 16% of all known vulnerabilities).

Severity (CVSS 4.0)6.0Medium

Exploit odds (30 days)0.2%top 83.9% of all CVEs

Exploited in the wildNo reportsCISA SSVC: none

Attack toolingNoneno public tooling known

Official description

Zulip is an open-source team collaboration tool. Prior to 12.0, With message_edit_history_visibility_policy set to "moves", /api/v1/messages/{id}/history still returns historical content values, allowing low-privilege users to recover text that was edited away from other users' messages. This vulnerability is fixed in 12.0.

Affected products (as reported)

Vendor	Product	Versions
zulip	zulip	< 12.0

Weakness: CWE-284 · Vector: 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

References

https://github.com/zulip/zulip/security/advisories/GHSA-jp8f-mvv6-89cr x_refsource_CONFIRM