CVE-2026-40300

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

MEDIUM
6.5
CVSS Score
Published: May 12, 2026 at 04:33 PM UTC
Updated: June 17, 2026 at 10:44 AM UTC
2 products affected across 1 vendorZulip ServerZulip

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Severity
MEDIUM6.5
Exploit prediction
EPSS 0.2%
SSVC
No known exploit

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Prior to 12.0, With message_edit_history_visibility_policy set to "moves", /api/v1/messages/{id}/history still returns historical content values, allowing low-privilege users to recover text that was edited away from other users' messages.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

Our own answer: ranges merged, affected separated from platform-only, with confidence and review flags.

v < 12.0
Affected range stops below 12.0, so it looks safe — our inference, not a vendor statement

Remediation

No guide yet

No remediation guidance has been written for this CVE yet. What the record does show:

References (1)

x_refsource_CONFIRMExploitVendor Advisory
Source: cverecord
https://github.com/zulip/zulip/security/advisories/GHSA-jp8f-mvv6-89cr

SSVC — Action Prioritization

SSVCNo known exploitNot automatablePartial impact

SSVC signals action urgency (what to patch first), separate from CVSS which measures severity.

CVSS

Attack Vector
NETWORK
Complexity
LOW
Privileges
LOW
User Interaction
NONE
Scope
UNCHANGED
Confidentiality
HIGH
Integrity
NONE
Availability
NONE
Vector?

Quick Info

StatusANALYZED
CWE
CWE-284NVD-CWE-noinfo

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