# CVE-2021-41101: CORS `Access-Control-Allow-Origin` settings are too lenient

> Lenient CORS settings allow attackers to exploit XSS on subdomains to access user cookies and interact with the Wire API.

- **Severity:** Medium 5.7 (`CVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:U/C:H/I:N/A:N`)
- **Exploited in the wild:** Not known
- **Login needed:** Any signed-in user
- **Attackable:** Over the internet
- **Victim action needed:** A user has to click or open something
- **Fix available:** No
- **Published:** 30 Sep 2021
- **Updated:** 4 Aug 2024
- **Also known as:** GHSA-v7xx-cx8m-g66p

## What is CVE-2021-41101?

CVE-2021-41101 is a medium-severity vulnerability in wireapp wire-server, published on 30 Sep 2021. Any signed-in user can exploit it over the network, and only if a user opens a file or follows a link.

### Official description

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).

Weakness: CWE-79 (Improper Neutralization of Input During Web Page Generation)

## Which versions are affected by CVE-2021-41101?

It affects 1 product.


Products: Wire Wire Server.

## How do I fix CVE-2021-41101?

No fix has been published for CVE-2021-41101 yet. Limit exposure of the affected software until one is available.

## Is CVE-2021-41101 being exploited?

There is no known exploitation of CVE-2021-41101 in the wild and no public exploit code.

## Other vulnerabilities in wireapp wire-server

- [CVE-2022-31122](https://insights.sbomify.com/CVE-2022-31122/): Auth bypass in wire-server (critical 9.8)
- [CVE-2021-21396](https://insights.sbomify.com/CVE-2021-21396/): Bulk list client endpoint exposes too much metadata about a client (medium 6.5)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2021-41101 and fix it if it is affected.

What it is: CVE-2021-41101 is a medium-severity vulnerability in wireapp wire-server, published on 30 Sep 2021. Any signed-in user can exploit it over the network, and only if a user opens a file or follows a link.
Exploitation: There is no known exploitation of CVE-2021-41101 in the wild and no public exploit code.

Affected product: wireapp wire-server. No package-level version data is available, so check the vendor advisory linked from the reference page.

Task:
1. Search the dependency manifests and lockfiles (for example package.json, package-lock.json, requirements.txt, poetry.lock, uv.lock, pom.xml, build.gradle, go.mod, Cargo.lock, Gemfile.lock) and any Dockerfiles for the affected packages, including transitive dependencies.
2. If an affected version is in use, upgrade it to the fixed version for its release line with the project's package manager, so the lockfile is regenerated. Prefer the smallest upgrade that fixes it.
3. If there is no fix, or the upgrade would break the build, do not guess: explain the risk and the safest workaround instead.
4. Run the tests and summarise what changed and why.
5. If nothing in the project is affected, say so and change nothing.

Reference: https://insights.sbomify.com/CVE-2021-41101/ (Markdown: https://insights.sbomify.com/CVE-2021-41101/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2021-41101
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2021-41101
- OSV: https://osv.dev/vulnerability/CVE-2021-41101

---
From sbomify Insights: https://insights.sbomify.com/CVE-2021-41101/
Summaries are generated and may contain mistakes; the official description above is the record.