# CVE-2021-40121: Cisco Identity Services Engine Cross-Site Scripting Vulnerabilities

> Attackers can execute arbitrary scripts in the web interface of Cisco ISE, potentially compromising user sessions.

- **Severity:** Medium 6.1 (`CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/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:** 21 Oct 2021
- **Updated:** 7 Nov 2024
- **Also known as:** GHSA-x2xf-qg7j-8h8x

## What is CVE-2021-40121?

CVE-2021-40121 is a medium-severity cross-site scripting vulnerability in Cisco Identity Services Engine, published on 21 Oct 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

Multiple vulnerabilities in the web-based management interface of Cisco Identity Services Engine (ISE) Software could allow an attacker to conduct a cross-site scripting (XSS) attack against a user of the interface. For more information about these vulnerabilities, see the Details section of this advisory.

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

## Which versions are affected by CVE-2021-40121?

It affects 1 product.


Products: Cisco Identity Services Engine.

## How do I fix CVE-2021-40121?

No fix has been published for CVE-2021-40121 yet. Limit exposure of the affected software until one is available.

## Is CVE-2021-40121 being exploited?

There is no known exploitation of CVE-2021-40121 in the wild and no public exploit code.

## Other vulnerabilities in Cisco Identity Services Engine

- [CVE-2026-76460](https://insights.sbomify.com/CVE-2026-76460/): Cisco Identity Services Engine Incorrect Use of Privileged APIs (critical 10.0, exploited in the wild)
- [CVE-2025-20337](https://insights.sbomify.com/CVE-2025-20337/): Cisco Identity Services Engine Injection (critical 10.0, exploited in the wild)
- [CVE-2025-20281](https://insights.sbomify.com/CVE-2025-20281/): Cisco Identity Services Engine Injection (critical 10.0, exploited in the wild)
- [CVE-2026-20130](https://insights.sbomify.com/CVE-2026-20130/): Cisco Identity Services Engine Hardening Release - Improper Neutralization Vulnerabilities (critical 10.0)
- [CVE-2026-20192](https://insights.sbomify.com/CVE-2026-20192/): Cisco Identity Services Engine Hardening Release - Access Control Vulnerabilities (critical 10.0)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2021-40121 and fix it if it is affected.

What it is: CVE-2021-40121 is a medium-severity cross-site scripting vulnerability in Cisco Identity Services Engine, published on 21 Oct 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-2021-40121 in the wild and no public exploit code.

Affected product: Cisco Identity Services Engine. 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-2021-40121/ (Markdown: https://insights.sbomify.com/CVE-2021-40121/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2021-40121
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2021-40121
- OSV: https://osv.dev/vulnerability/CVE-2021-40121

---
From sbomify Insights: https://insights.sbomify.com/CVE-2021-40121/
Summaries are generated and may contain mistakes; the official description above is the record.