# CVE-2021-1567: Cisco AnyConnect Secure Mobility Client for Windows with VPN Posture (HostScan) Module DLL Hijacking Vulnerability

> Local attackers can execute arbitrary code with SYSTEM privileges via DLL hijacking in Cisco AnyConnect if the HostScan module is installed.

- **Severity:** High 7.0 (`CVSS:3.1/AV:L/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:H`)
- **Exploited in the wild:** Not known
- **Login needed:** Any signed-in user
- **Attackable:** Local or same network only
- **Victim action needed:** Not needed
- **Fix available:** No
- **Published:** 16 Jun 2021
- **Updated:** 7 Nov 2024
- **Also known as:** GHSA-wxfr-9v84-73vc

## What is CVE-2021-1567?

CVE-2021-1567 is a high-severity vulnerability in Cisco Anyconnect Secure Mobility Client, published on 16 Jun 2021. It can only be exploited from the same machine or local network, with no action from the victim.

### Official description

A vulnerability in the DLL loading mechanism of Cisco AnyConnect Secure Mobility Client for Windows could allow an authenticated, local attacker to perform a DLL hijacking attack on an affected device if the VPN Posture (HostScan) Module is installed on the AnyConnect client. This vulnerability is due to a race condition in the signature verification process for DLL files that are loaded on an affected device. An attacker could exploit this vulnerability by sending a series of crafted interprocess communication (IPC) messages to the AnyConnect process. A successful exploit could allow the attacker to execute arbitrary code on the affected device with SYSTEM privileges. To exploit this vulnerability, the attacker must have valid credentials on the Windows system.

Weakness: CWE-427 (Uncontrolled Search Path Element), CWE-367 (Time-of-check Time-of-use (TOCTOU) Race Condition)

## Which versions are affected by CVE-2021-1567?

It affects 1 product.


Products: Cisco Anyconnect Secure Mobility Client.

## How do I fix CVE-2021-1567?

No fix has been published for CVE-2021-1567 yet. Limit exposure of the affected software until one is available.

## Is CVE-2021-1567 being exploited?

There is no known exploitation of CVE-2021-1567 in the wild and no public exploit code.

## Other vulnerabilities in Cisco Anyconnect Secure Mobility Client

- [CVE-2020-3433](https://insights.sbomify.com/CVE-2020-3433/): Cisco AnyConnect Secure Mobility Client for Windows DLL Hijacking (high 7.8, exploited in the wild)
- [CVE-2020-3153](https://insights.sbomify.com/CVE-2020-3153/): Cisco AnyConnect Secure Mobility Client for Windows Uncontrolled Search Path (medium 6.5, exploited in the wild)
- [CVE-2012-3088](https://insights.sbomify.com/CVE-2012-3088/): Security feature bypass in n/a (critical 9.3)
- [CVE-2012-2493](https://insights.sbomify.com/CVE-2012-2493/): Code injection in n/a (critical 9.3)
- [CVE-2011-2040](https://insights.sbomify.com/CVE-2011-2040/): Code injection in n/a (critical 9.3)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2021-1567 and fix it if it is affected.

What it is: CVE-2021-1567 is a high-severity vulnerability in Cisco Anyconnect Secure Mobility Client, published on 16 Jun 2021. It can only be exploited from the same machine or local network, with no action from the victim.
Exploitation: There is no known exploitation of CVE-2021-1567 in the wild and no public exploit code.

Affected product: Cisco Anyconnect Secure Mobility Client. 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-2021-1567/ (Markdown: https://insights.sbomify.com/CVE-2021-1567/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2021-1567
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2021-1567
- OSV: https://osv.dev/vulnerability/CVE-2021-1567

---
From sbomify Insights: https://insights.sbomify.com/CVE-2021-1567/
Summaries are generated and may contain mistakes; the official description above is the record.