Vulnerability CVE-2021-41115


Published: 2021-10-07   Modified: 2021-10-08

Description:
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).

Type:

NVD-CWE-Other

CVSS2 => (AV:N/AC:L/Au:S/C:N/I:N/A:P)

CVSS Base Score
Impact Subscore
Exploitability Subscore
4/10
2.9/10
8/10
Exploit range
Attack complexity
Authentication
Remote
Low
Single time
Confidentiality impact
Integrity impact
Availability impact
None
None
Partial
Affected software
Zulip -> Zulip 

 References:
https://github.com/zulip/zulip/security/advisories/GHSA-4h36-mqfq-42jg
https://securitylab.github.com/advisories/GHSL-2021-118-zulip-zulip/
https://github.com/zulip/zulip/commit/e2d303c1bb5f538d17dc3d9134bc8858bdece781

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