Vulnerability Details : 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 category: Denial of service
Products affected by CVE-2021-41115
- cpe:2.3:a:zulip:zulip:*:*:*:*:*:*:*:*
Exploit prediction scoring system (EPSS) score for CVE-2021-41115
0.16%
Probability of exploitation activity in the next 30 days
EPSS Score History
~ 52 %
Percentile, the proportion of vulnerabilities that are scored at or less
CVSS scores for CVE-2021-41115
| Base Score | Base Severity | CVSS Vector | Exploitability Score | Impact Score | Score Source | First Seen |
|---|---|---|---|---|---|---|
|
4.0
|
MEDIUM | AV:N/AC:L/Au:S/C:N/I:N/A:P |
8.0
|
2.9
|
NIST | |
|
6.5
|
MEDIUM | CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H |
2.8
|
3.6
|
NIST | |
|
4.3
|
MEDIUM | CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:L |
2.8
|
1.4
|
GitHub, Inc. |
CWE ids for CVE-2021-41115
-
The product does not properly control the allocation and maintenance of a limited resource, thereby enabling an actor to influence the amount of resources consumed, eventually leading to the exhaustion of available resources.Assigned by:
- nvd@nist.gov (Primary)
- security-advisories@github.com (Secondary)
-
The product compares two entities in a security-relevant context, but the comparison is incorrect, which may lead to resultant weaknesses.Assigned by: nvd@nist.gov (Primary)
-
The product uses a regular expression with an inefficient, possibly exponential worst-case computational complexity that consumes excessive CPU cycles.Assigned by:
- nvd@nist.gov (Primary)
- security-advisories@github.com (Secondary)
References for CVE-2021-41115
-
https://github.com/zulip/zulip/security/advisories/GHSA-4h36-mqfq-42jg
Regular expression denial-of-service in linkifiers · Advisory · zulip/zulip · GitHubPatch;Third Party Advisory
-
https://github.com/zulip/zulip/commit/e2d303c1bb5f538d17dc3d9134bc8858bdece781
CVE-2021-41115: Use re2 for user-supplied linkifier patterns. · zulip/zulip@e2d303c · GitHubPatch;Third Party Advisory
-
https://securitylab.github.com/advisories/GHSL-2021-118-zulip-zulip/
GitHub Security Lab | Securing the world’s software, togetherExploit;Third Party Advisory
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