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

MITRE NVD CVE.ORG JSON API

Summary

CVECVE-2026-97701
StatePUBLISHED
AssignerGitHub_M
Source PriorityCVE Program / NVD first with legacy fallback
Published2026-11-04 19:17:41 UTC
Updated2026-11-04 19:17:41 UTC
DescriptionZulip 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.

Risk And Classification

Primary CVSS: v3.1 6.5 MEDIUM from [email protected]

CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H

Problem Types: CWE-770 | CWE-770 CWE-770: Allocation of Resources Without Limits or Throttling

VersionSourceTypeScoreSeverityVector
3.1[email protected]Secondary6.5MEDIUMCVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H
3.1CNADECLARED6.5MEDIUMCVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H

CVSS v3.1 Breakdown

Attack Vector
Network
Attack Complexity
Low
Privileges Required
Low
User Interaction
None
Scope
Unchanged
Confidentiality
None
Integrity
None
Availability
High

CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H

Vendor Declared Affected Products

SourceVendorProductVersionPlatforms
CNA Zulip Zulip affected < 12.2 Not specified

References

ReferenceSourceLinkTags
github.com/zulip/zulip/commit/31773c77c501391ede0fa8ec727f39508664e0ae [email protected] github.com
github.com/zulip/zulip/releases/tag/12.2 [email protected] github.com
github.com/zulip/zulip/pull/39913 [email protected] github.com
github.com/zulip/zulip/security/advisories/GHSA-m257-w4r5-5rmf [email protected] github.com
github.com/zulip/zulip/commit/4d94dd2ee6337a4b3351694dd314a45d3fe11031 [email protected] github.com
zulip.readthedocs.io/en/latest/overview/changelog.html [email protected] zulip.readthedocs.io
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