# CVE-2021-40836: Denial-of-Service (DoS) Vulnerability

> Remote attackers can cause denial-of-service in F-Secure antivirus engines by sending malicious Microsoft Outlook PST files for scanning.

- **Severity:** Medium 4.6 (`CVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:U/C:L/I:N/A:L`)
- **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:** 22 Dec 2021
- **Updated:** 4 Aug 2024
- **Also known as:** GHSA-mvh9-66vv-hxxf

## What is CVE-2021-40836?

CVE-2021-40836 is a medium-severity denial of service vulnerability in F-Secure endpoint protection products on Windows and Mac. F-Secure Linux Security (32-bit)  F-Secure Linux Security 64  F-Secure Atlant & F-Secure Internet Gatekeeper, published on 22 Dec 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

A vulnerability affecting F-Secure antivirus engine was discovered whereby scanning MS outlook .pst files can lead to denial-of-service. The vulnerability can be exploited remotely by an attacker. A successful attack will result in denial-of-service of the antivirus engine.

## Which versions are affected by CVE-2021-40836?

It affects 6 products.


Products: F-Secure Atlant, F-Secure Elements Endpoint Detection and Response, F-Secure Elements Endpoint Protection, F-Secure Internet Gatekeeper, F-Secure Linux Security, F-Secure Linux Security 64.

## How do I fix CVE-2021-40836?

No fix has been published for CVE-2021-40836 yet. Limit exposure of the affected software until one is available.

## Is CVE-2021-40836 being exploited?

There is no known exploitation of CVE-2021-40836 in the wild and no public exploit code.

## Other vulnerabilities in F-Secure endpoint protection products on Windows and Mac. F-Secure Linux Security (32-bit)  F-Secure Linux Security 64  F-Secure Atlant & F-Secure Internet Gatekeeper

- [CVE-2023-43766](https://insights.sbomify.com/CVE-2023-43766/): Privilege escalation in n/a (high 7.8)
- [CVE-2023-49322](https://insights.sbomify.com/CVE-2023-49322/): Denial of service in n/a (high 7.5)
- [CVE-2023-43760](https://insights.sbomify.com/CVE-2023-43760/): Denial of service in n/a (high 7.5)
- [CVE-2023-43761](https://insights.sbomify.com/CVE-2023-43761/): Denial of service in n/a (high 7.5)
- [CVE-2023-43765](https://insights.sbomify.com/CVE-2023-43765/): Denial of service in n/a (high 7.5)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2021-40836 and fix it if it is affected.

What it is: CVE-2021-40836 is a medium-severity denial of service vulnerability in F-Secure endpoint protection products on Windows and Mac. F-Secure Linux Security (32-bit)  F-Secure Linux Security 64  F-Secure Atlant & F-Secure Internet Gatekeeper, published on 22 Dec 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-2021-40836 in the wild and no public exploit code.

Affected product: F-Secure endpoint protection products on Windows and Mac. F-Secure Linux Security (32-bit)  F-Secure Linux Security 64  F-Secure Atlant & F-Secure Internet Gatekeeper. 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-2021-40836/ (Markdown: https://insights.sbomify.com/CVE-2021-40836/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2021-40836
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2021-40836
- OSV: https://osv.dev/vulnerability/CVE-2021-40836

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From sbomify Insights: https://insights.sbomify.com/CVE-2021-40836/
Summaries are generated and may contain mistakes; the official description above is the record.