Message Length Limit Bypass in Zulip Collaboration Tool
CVE-2026-97701

6.5MEDIUM

Key Information:

Vendor

Zulip

Status
Zulip
Vendor
CVE Published:
4 November 2026

What is CVE-2026-97701?

Zulip Server prior to version 12.2 contains a vulnerability in the /messages/render endpoint, allowing authenticated users to submit excessive Markdown content. This bypasses the enforced message length limit, leading to significant backend CPU consumption. The overload can adversely affect Markdown rendering performance and result in availability issues for other users. Upgrading to version 12.2 resolves this concern.

Affected Version(s)

zulip < 12.2

References

https://github.com/zulip/zulip/security/advisories/GHSA-m...
x_refsource_CONFIRM
https://github.com/zulip/zulip/pull/39913
x_refsource_MISC
https://github.com/zulip/zulip/commit/31773c77c501391ede0...
x_refsource_MISC

CVSS V3.1

Score:
6.5
Severity:
MEDIUM
Confidentiality:
None
Integrity:
None
Availability:
None
Attack Vector:
Network
Attack Complexity:
Low
Privileges Required:
Low
User Interaction:
None
Scope:
Unchanged

Timeline

  • Vulnerability published

  • Vulnerability Reserved

.