Vulnerability identifier: #VU30742

Vulnerability risk: Medium

CVSSv3.1: 5.7 [CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H/E:U/RL:O/RC:C]

CVE-ID: CVE-2019-16215

CWE-ID: CWE-400

Exploitation vector: Network

Exploit availability: No

Vulnerable software:
Zulip Server
Web applications / Other software

Vendor: Zulip

Description

The vulnerability allows a remote authenticated user to perform a denial of service (DoS) attack.

The Markdown parser in Zulip server before 2.0.5 used a regular expression vulnerable to exponential backtracking. A user who is logged into the server could send a crafted message causing the server to spend an effectively arbitrary amount of CPU time and stall the processing of future messages.

Mitigation
Install update from vendor's website.

Vulnerable software versions

Zulip Server: 2.0.0 - 2.0.4

---

External links
http://blog.zulip.org/2019/09/11/zulip-server-2-0-5-security-release/
http://github.com/zulip/zulip/commit/5797f013b3be450c146a4141514bda525f2f1b51

---

Q & A

Can this vulnerability be exploited remotely?

Yes. This vulnerability can be exploited by a remote authenticated user via the Internet.

Is there known malware, which exploits this vulnerability?

No. We are not aware of malware exploiting this vulnerability.