Vulnerability · Published Nov 4, 2026 · Assigned by GitHub_M

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

Medium 6.5

In plain English

A medium-severity resource allocation without limits in zulip from zulip. There are no confirmed reports of exploitation so far. The chance it is exploited in the next 30 days is estimated at 0.4% (higher than 38% of all known vulnerabilities).

Severity (CVSS 3.1)6.5Medium

Exploit odds (30 days)0.4%top 62.3% of all CVEs

Exploited in the wildNo reportsCISA SSVC: none

Attack toolingNoneno public tooling known

Official 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.

Affected products (as reported)

Vendor	Product	Versions
zulip	zulip	< 12.2

Weakness: CWE-770 · Vector: CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H

References

https://github.com/zulip/zulip/security/advisories/GHSA-m257-w4r5-5rmf x_refsource_CONFIRM
https://github.com/zulip/zulip/pull/39913 x_refsource_MISC
https://github.com/zulip/zulip/commit/31773c77c501391ede0fa8ec727f39508664e0ae x_refsource_MISC
https://github.com/zulip/zulip/commit/4d94dd2ee6337a4b3351694dd314a45d3fe11031 x_refsource_MISC
https://github.com/zulip/zulip/releases/tag/12.2 x_refsource_MISC
https://zulip.readthedocs.io/en/latest/overview/changelog.html#zulip-server-12-2 x_refsource_MISC