Is CVE-2026-97701 exploited in the wild?

No. Junglewise Threat Intelligence has no report of CVE-2026-97701 being exploited in the wild.

How severe is CVE-2026-97701?

Medium severity, with a CVSS score of 6.5, published 4 November 2026.

Is there a fix for CVE-2026-97701?

Yes: fixed in 12.2. Junglewise finds every place you run it, drafts the upgrade and applies it once you approve.

How is CVE-2026-97701 attacked?

It is attacked over the network.

Am I affected by CVE-2026-97701?

Check whether you run Zulip Server at an affected version. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.

CVE-2026-97701: Zulip Server missing content length limit in render endpoint

CVE-2026-97701 · Severity: medium · CVSS 6.5 · Published 2026-11-04

Zulip Server is a team collaboration and messaging platform used by organizations to communicate internally. An authenticated user can send excessively large Markdown content to a rendering endpoint, causing the backend to consume disproportionate CPU resources and degrading performance or availability for other users. This could lead to service disruptions or temporary unavailability.

Technologies: Zulip Server. Vendors: Zulip.

Quick answers

Is CVE-2026-97701 exploited in the wild?: No. Junglewise Threat Intelligence has no report of CVE-2026-97701 being exploited in the wild.
How severe is CVE-2026-97701?: Medium severity, with a CVSS score of 6.5, published 4 November 2026.
Which products and versions are affected?: Zulip Server through 12.1.
Is there a fix for CVE-2026-97701?: Yes: fixed in 12.2. Junglewise finds every place you run it, drafts the upgrade and applies it once you approve.
How is CVE-2026-97701 attacked?: It is attacked over the network.
Am I affected by CVE-2026-97701?: Check whether you run Zulip Server at an affected version. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.

How to fix

Fixed in: 12.2

Technical details

The POST /messages/render endpoint in Zulip Server versions through 12.1 lacks the content length validation applied to normal message send and edit operations, allowing authenticated attackers to submit Markdown content up to the server's body-size limit. Processing large payloads causes excessive CPU consumption in the Markdown rendering engine; repeated or concurrent requests amplify the impact. The fix adds StringConstraints with MAX_MESSAGE_LENGTH validation to the content parameter.

Affected products

Zulip Server through 12.1

Timeline

2026-11-04: disclosed

References

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