{"id":"CVE-2021-41115","details":"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).","aliases":["GHSA-4h36-mqfq-42jg"],"modified":"2026-08-07T19:48:38.299365Z","published":"2021-10-07T23:15:08.027Z","references":[{"type":"FIX","url":"https://github.com/zulip/zulip/commit/e2d303c1bb5f538d17dc3d9134bc8858bdece781"},{"type":"FIX","url":"https://github.com/zulip/zulip/security/advisories/GHSA-4h36-mqfq-42jg"},{"type":"EVIDENCE","url":"https://securitylab.github.com/advisories/GHSL-2021-118-zulip-zulip/"}],"affected":[{"ranges":[{"type":"GIT","repo":"https://github.com/zulip/zulip","events":[{"introduced":"0"},{"fixed":"4e724c1ec659086740d02eeab2789c4b07c6d822"},{"fixed":"e2d303c1bb5f538d17dc3d9134bc8858bdece781"}],"database_specific":{"extracted_events":[{"introduced":"0"},{"fixed":"4.7"}],"source":["CPE_RANGE","REFERENCES"],"cpe":"cpe:2.3:a:zulip:zulip:*:*:*:*:*:*:*:*"}}],"versions":["4.6","4.5","4.4","4.3","4.2","4.1","4.0","shared-0.0.5","shared-0.0.4","shared-0.0.3","4.0-dev","3.0","3.0-rc2","3.0-rc1","3.0-dev","2.2-dev","2.1.0","2.1.0-rc1","shared-0.0.2","shared-0.0.1","2.0.0","2.1-dev","2.0.0-rc1","1.9.0","1.9.0-rc3","1.9.0-rc2","1.8.0","1.8.0-rc1","1.7.0","1.6.0","1.5.0","1.4.0","1.3.13","1.3.11","1.3.10","1.3.9","1.3.8","1.3.7","1.3.6","1.3.5","1.3.4","1.3.3","1.3.2","1.3.1","1.3.0","enterprise-1.2.0","enterprise-1.1.5"],"database_specific":{"source":"https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2021-41115.json"}}],"schema_version":"1.8.0","severity":[{"type":"CVSS_V3","score":"CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H"}]}