Zulip: Missing content-length limit on POST /messages/render allows denial-of-service via oversized requests
Written by anthropic/claude-haiku-5.5 from the sources below. Verify against them.
- Exploited
- No known exploitation
- Fix
- Fixed in 12.2
- Who is exposed
- Not reported
Do first: Upgrade to a fixed version: 12.2.
- Exploitation0/40No signal
- Exposure3/25Reachable over the network · Data gap: No advisory context yet
- Reach?/20Reach: unknown (data gap). No tracked technology or package matched
- Severity6.5/10CVSS 6.5
- No patch0/5No signal
What would change the score
- Would score about 65 if added to CISA KEV
- Would score about 60 if CISA's SSVC rates exploitation active
- Would score about 29 if advisories confirm default setups are exposed
CVE-2026-97701 is not in CISA's Known Exploited Vulnerabilities (KEV) catalog. No public exploit code is tracked. It is rated CVSS 6.5 (medium) and affects zulip; fixed in 12.2.
- Last modified
- Where the record stands: published, rejected by its publisher, or superseded by another id.What do these mean? →
- Published
- Whether CISA lists it in its Known Exploited Vulnerabilities catalog: proof that attackers are using it.What do these mean? →
- Not listed in CISA KEV
- A 0-100 score for how much a CVE matters across the industry: exploitation, exposure, how widely the software is used, severity and whether a fix exists.What do these mean? →
- 10/100 · provisional
- Fix
- Fixed in 12.2
- Whether working attack code is public (Exploit-DB, Metasploit, Nuclei or GitHub). Public code makes attacks easier.What do these mean? →
- None on Exploit-DB, Metasploit or GitHub
- Exploitation: none
- Automatable: no
- Technical impact: partial
Summary
Zulip Server, an open-source team collaboration tool, is affected by a flaw in its Markdown rendering endpoint that lets an attacker cause denial of service. An attacker who has a logged-in account can reach it remotely over the network and submit oversized Markdown that overloads the server's CPU, degrading availability for other users.
Read the original 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.
What to do
Upgrade to a fixed version: 12.2.
Timeline
- CVE published
- First seen by cve.now
- CISA SSVC assessment
Exploitation: none · Automatable: no · Technical impact: partial
- Record last updated
Affected versions
- zulip zulip
fixed in 12.2
Evidence 6
- Advisory
- Repository
- Repository
- Repository
- Repository
- Link
Corrections
None so far.
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Questions about CVE-2026-97701
Is CVE-2026-97701 being exploited?
It is not in CISA's Known Exploited Vulnerabilities catalog, and CISA's SSVC assessment does not mark exploitation as active. That does not mean it has not been attacked: vendors and researchers can report attacks before CISA lists them. No public exploit code is tracked.Source: cve.now feed data
Which versions are affected by CVE-2026-97701?
zulip: before 12.2.Source: cve.now feed data
How do I fix CVE-2026-97701?
Upgrade to a fixed version: 12.2.Source: cve.now feed data