CVE-2021-41101: CORS `Access-Control-Allow-Origin` settings are too lenient
wire-server is an open-source back end for Wire, a secure collaboration platform. Before version 2.106.0, the CORS Access-Control-Allow-Origin header set by nginz is set for all subdomains of .wire.com (including wire.com). This means that if somebody were to find an XSS vector in any of the subdomains, they could use it to talk to the Wire API using the user's Cookie. A patch does not exist, but a workaround does. To make sure that a compromise of one subdomain does not yield access to the cookie of another, one may limit the Access-Control-Allow-Origin header to apps that actually require the cookie (account-pages, team-settings and the webapp).
Affected Software
Remediation
Recommended actions to resolve this vulnerability, in priority order.
- Configuration
For nginz instances using the default CORS behavior (before 2.106.0), restrict the CORS Access-Control-Allow-Origin header so it is not set for all subdomains of .wire.com (including wire.com). Configure it to only allow the specific apps that require the user's cookie: account-pages, team-settings, and the webapp.
nginz (CORS Access-Control-Allow-Origin for Wire domain) Access-Control-Allow-Origin = Limit to apps that actually require the cookie (account-pages, team-settings, and the webapp)
Event History
Frequently Asked Questions
What is the vulnerability ID for this issue?
The vulnerability ID for this issue is CVE-2021-41101.
What is the severity of CVE-2021-41101?
The severity of CVE-2021-41101 is medium with a CVSS score of 5.7.
What is the affected software?
The affected software is Wire Server before version 2.106.0.
What is the Common Weakness Enumeration (CWE) ID for this vulnerability?
The CWE ID for this vulnerability is CWE-79.
Is there a reference for this vulnerability?
Yes, you can find more information about the vulnerability in the Wire Server security advisory on GitHub: https://github.com/wireapp/wire-server/security/advisories/GHSA-v7xx-cx8m-g66p