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

Quick assessment

Affected
zulip zulip
Exploitation
No confirmed in-the-wild exploitation; assess based on exposure
Recommended action
Check the vendor advisory and references for a fixed version. If immediate upgrade is impossible, restrict exposure and increase monitoring.

Zulip 是一款开源的团队协作工具。在 Zulip Server 12.1 及更早版本中，经过身份验证的 接口在渲染 参数时，未执行消息发送和编辑操作中通常采用的消息长度限制。经过身份验证的用户可以提交高达服务器请求体大小限制的 Markdown 内容，从而导致后端 CPU 消耗不成比例地增加；若进行重复或并发请求，可能会降低 Markdown 渲染性能，甚至影响其他用户的后端服务可用性。该问题已在 12.2 版本中修复。

CVSS 6.5 · Medium

Possible ATT&CK Techniques 1 AI

T1499.003 · Application Exhaustion Flood

Affected Version Matrix 1

VendorProduct Version RangeStatus
zulip zulip < 12.2 affected
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I. Basic Information for CVE-2026-97701

Vulnerability Information
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Vulnerability Title
Zulip: Missing content-length limit on POST /messages/render allows denial-of-service via oversized requests
Source: CVE Program / CVE List V5
Vulnerability Description
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.
Source: CVE Program / CVE List V5
CVSS Information
CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H
Source: CVE Program / CVE List V5
Vulnerability Type
不加限制或调节的资源分配
Source: CVE Program / CVE List V5

Affected Products

Vendor Product Affected Versions CPE Subscribe
zulip zulip < 12.2 -

II. Public POCs for CVE-2026-97701

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III. Intelligence Information for CVE-2026-97701

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Patches & Fixes for CVE-2026-97701 (1)

Other References for CVE-2026-97701 (1)

Other References for CVE-2026-97701 (4)

Same Patch Batch · zulip · 2026-11-04 · 3 CVEs total

CVE-2026-115474 6.5 MEDIUM Zulip: Saving a draft DM to a user bypasses can_access_all_users_group permission
CVE-2026-115574 5.3 MEDIUM Zulip: Custom profile fields can be read by logged-out visitors in organization with web-p

IV. Related Vulnerabilities

Same product: zulip
Same vendor: zulip
Same weakness: CWE-770