# CVE-2026-97701: Zulip: Missing content-length limit on POST /messages/render allows denial-of-service via oversized requests

Status: published. Published: 2026-11-04. Updated: 2026-11-04.

Zulip is an open-source team collaboration tool. In Zulip Server versions through 12.1, the authenticated POST /messages/render endpoint renders the content parameter without enforcing the normal message length limit used by message send and edit operations. An authenticated user can submit Markdown up to the server body-size limit, causing disproportionate backend CPU consumption, and repeated or concurrent requests can degrade Markdown rendering performance or backend availability for other users. This issue is fixed in version 12.2.

## Remediation

No remediation reported in collected sources

## Affected products and versions

- zulip / zulip: < 12.2 (affected). Source: CNA: GitHub_M

## Severity and prioritization

- CVSS 3.1: 6.5 (medium); CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H; source: CNA: GitHub_M

- CISA KEV: No listing in collected sources

- EPSS: Not available

- SSVC: exploitation none; automatable no; technical impact partial; source ADP: CISA-ADP

- Weaknesses: CWE-770

## Exploit evidence

No exploit evidence in collected sources. This is not proof of no exploitation.

## References

- https://github.com/zulip/zulip/security/advisories/GHSA-m257-w4r5-5rmf (CNA: GitHub_M; x_refsource_CONFIRM)

- https://github.com/zulip/zulip/pull/39913 (CNA: GitHub_M; x_refsource_MISC)

- https://github.com/zulip/zulip/commit/31773c77c501391ede0fa8ec727f39508664e0ae (CNA: GitHub_M; x_refsource_MISC)

- https://github.com/zulip/zulip/commit/4d94dd2ee6337a4b3351694dd314a45d3fe11031 (CNA: GitHub_M; x_refsource_MISC)

- https://github.com/zulip/zulip/releases/tag/12.2 (CNA: GitHub_M; x_refsource_MISC)

- https://zulip.readthedocs.io/en/latest/overview/changelog.html#zulip-server-12-2 (CNA: GitHub_M; x_refsource_MISC)

## Provenance

- CNA: GitHub_M: https://www.cve.org/CVERecord?id=CVE-2026-97701; retrieved 2026-11-04; source updated 2026-11-04

Revision: 92015b789c3271806b741129c4ba19e8b25e145b7355c70c9fe9332faad5c55b

Canonical: https://y2.dev/cve/CVE-2026-97701

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