CVE-2022-31017: Expression Always True vulnerability in Zulip Server

Severity: low (CVSS 2.6 v3.1)
Exploited in the wild: not listed in CISA KEV
EPSS: 0.6% probability of exploitation in the next 30 days
Public exploit or detection template: none known
Published: 2022-06-25 · updated 2026-06-17
Weakness: CWE-571

Description

Zulip is an open-source team collaboration tool. Versions 2.1.0 through and including 5.2 are vulnerable to a logic error. A stream configured as private with protected history, where new subscribers should not be allowed to see messages sent before they were subscribed, when edited causes the server to incorrectly send an API event that includes the edited message to all of the stream’s current subscribers. This API event is ignored by official clients, but can be observed by using a modified client or the browser’s developer tools. This bug will be fixed in Zulip Server 5.3. There are no known workarounds.

Affected products

zulip: from 2.1.0 before 5.3 — fixed in 5.3

How to fix

Upgrade to a fixed version: zulip 5.3. Check the vendor advisory for mitigations.

References

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