Medium severity · published May 12, 2026
CVE-2026-40300
Zulip: Message edit history visible in "moves only" policy through /api/v1/messages/{id}/history
6.5
CVSS
0.2%
EPSS
No
On KEV
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Prior to 12.0, With message_edit_history_visibility_policy set to "moves", /api/v1/messages/{id}/history still returns historical content values, allowing low-privilege users to recover text that was edited away from other users' messages.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.
CVSS vector
CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:N/A:N
Attack vector
Network
Complexity
Low
Privileges
Low
User interaction
None
Confidentiality
High
Integrity
None
Availability
None
Scope
Unchanged
Exploitation
Is it being used?
Exploit prediction (EPSS)0.2% · higher than 16% of CVEs
Exploited in the wildNo evidence yet
CISA KEVNot listed
Ransomware campaign useNot known
Affected products
Which versions
ZU
zulip · zulip
< 12.0 · source: vendor
ZS
Zulip Server · Zulip
10.0 · source: NVD
References
NVD
https://nvd.nist.gov/vuln/detail/CVE-2026-40300
CVE.org
https://www.cve.org/CVERecord?id=CVE-2026-40300
Exploit
https://github.com/zulip/zulip/security/advisories/GHSA-jp8f-mvv6-89cr
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