# CVE-2021-22920: Auth bypass in Citrix ADC, Citrix Gateway

> Attackers can hijack SAML authentication to steal valid user sessions, leading to account takeover on Citrix ADC and Gateway devices.

- **Severity:** Medium 6.5 (`CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:N/A:N`)
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Over the internet
- **Victim action needed:** A user has to click or open something
- **Fix available:** No
- **Published:** 5 Aug 2021
- **Updated:** 3 Aug 2024
- **Also known as:** GHSA-5w66-9x5w-m57v

## What is CVE-2021-22920?

CVE-2021-22920 is a medium-severity authentication bypass vulnerability in Citrix ADC, Citrix Gateway, published on 5 Aug 2021. An attacker can exploit it over the internet without logging in, and only if a user opens a file or follows a link.

### Official description

A vulnerability has been discovered in Citrix ADC (formerly known as NetScaler ADC) and Citrix Gateway (formerly known as NetScaler Gateway), and Citrix SD-WAN WANOP Edition models 4000-WO, 4100-WO, 5000-WO, and 5100-WO. These vulnerabilities, if exploited, could lead to a phishing attack through a SAML authentication hijack to steal a valid user session.

Weakness: CWE-284 (Improper Access Control)

## Which versions are affected by CVE-2021-22920?

It affects 2 products.


Products: Citrix Application Delivery Management, Citrix Gateway.

## How do I fix CVE-2021-22920?

No fix has been published for CVE-2021-22920 yet. Limit exposure of the affected software until one is available.

## Is CVE-2021-22920 being exploited?

There is no known exploitation of CVE-2021-22920 in the wild and no public exploit code.

## Other vulnerabilities in Citrix ADC, Citrix Gateway

- [CVE-2019-9548](https://insights.sbomify.com/CVE-2019-9548/): Missing authorization in n/a (critical 10.0)
- [CVE-2019-17366](https://insights.sbomify.com/CVE-2019-17366/): Missing authorization in n/a (high 8.8)
- [CVE-2022-27511](https://insights.sbomify.com/CVE-2022-27511/): Privilege escalation in Citrix Application Delivery Management (Citrix ADM) (high 8.1)
- [CVE-2022-27512](https://insights.sbomify.com/CVE-2022-27512/): Temporary disruption of the ADM license service (medium 5.3)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2021-22920 and fix it if it is affected.

What it is: CVE-2021-22920 is a medium-severity authentication bypass vulnerability in Citrix ADC, Citrix Gateway, published on 5 Aug 2021. An attacker can exploit it over the internet without logging in, and only if a user opens a file or follows a link.
Exploitation: There is no known exploitation of CVE-2021-22920 in the wild and no public exploit code.

Affected product: Citrix ADC, Citrix Gateway. 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-2021-22920/ (Markdown: https://insights.sbomify.com/CVE-2021-22920/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2021-22920
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2021-22920
- OSV: https://osv.dev/vulnerability/CVE-2021-22920

---
From sbomify Insights: https://insights.sbomify.com/CVE-2021-22920/
Summaries are generated and may contain mistakes; the official description above is the record.