Resource exhaustion in Zulip
CVE-2021-41115
Zulip is an open source team chat server. In affected versions Zulip allows organization administrators on a server to configure "linkifiers" that automatically create links from messages that users send, detected via arbitrary regular expressions. Malicious organization administrators could subject the server to a denial-of-service via regular expression complexity attacks; most simply, by configuring a quadratic-time regular expression in a linkifier, and sending messages that exploited it. A regular expression attempted to parse the user-provided regexes to verify that they were safe from ReDoS -- this was both insufficient, as well as _itself_ subject to ReDoS if the organization administrator entered a sufficiently complex invalid regex. Affected users should [upgrade to the just-released Zulip 4.7](https://zulip.readthedocs.io/en/latest/production/upgrade-or-modify.html#upgrading-to-a-release), or [`main`](https://zulip.readthedocs.io/en/latest/production/upgrade-or-modify.html#upgrading-from-a-git-repository).
Vulnerability class: DoS (Denial of Service)
Published · last modified .
CVSS v3 metric
CVSS v3 base score 4.3 (Medium). Vector: CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:L.
EPSS exploit prediction
EPSS: 0.017 (76.8th percentile), scored .
Low probability of exploitation in the next 30 days, but still tracked. 77th percentile — 76.8% of CVEs in the catalogue have a lower EPSS than this one. How to read EPSS.
EPSS over last 30 days · oldest: 0.017 · newest: 0.017 · change: 0.000
Affected products
- Zulip — versions < 4.7
Weakness classification (CWE)
References
- github.com/zulip/zulip/security/advisories/GHSA-4h36-mqfq-42jg (Patch, Third Party Advisory)
- github.com/zulip/zulip/commit/e2d303c1bb5f538d17dc3d9134bc8858bdece781 (Patch, Third Party Advisory)
- securitylab.github.com/advisories/GHSL-2021-118-zulip-zulip/ (Exploit, Third Party Advisory)
Frequently asked questions
- What is CVE-2021-41115?
- CVE-2021-41115 is a medium-severity vulnerability in Zulip, classified under Uncontrolled Resource Consumption. CVSS score: 4.3/10. Published 2021-10-07.
- How severe is CVE-2021-41115?
- Medium severity. CVSS v3 base score is 4.3 out of 10.