# CVE-2022-39956: Security feature bypass in ModSecurity Core Rule Set

> Attackers can bypass ModSecurity Core Rule Set detection for multipart requests using specific character encodings, allowing malicious payloads to reach the backend.

- **Severity:** High 7.3 (`CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:L/A:L`)
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** Yes
- **Published:** 20 Sep 2022
- **Updated:** 3 Nov 2025
- **Also known as:** DEBIAN-CVE-2022-39956, GHSA-5xc6-pmr2-qj78, UBUNTU-CVE-2022-39956

## What is CVE-2022-39956?

CVE-2022-39956 is a high-severity vulnerability in Debian Debian Linux, published on 20 Sep 2022. An attacker can exploit it over the internet without logging in, with no action from the victim.

### Official description

The OWASP ModSecurity Core Rule Set (CRS) is affected by a partial rule set bypass for HTTP multipart requests by submitting a payload that uses a character encoding scheme via the Content-Type or the deprecated Content-Transfer-Encoding multipart MIME header fields that will not be decoded and inspected by the web application firewall engine and the rule set. The multipart payload will therefore bypass detection. A vulnerable backend that supports these encoding schemes can potentially be exploited. The legacy CRS versions 3.0.x and 3.1.x are affected, as well as the currently supported versions 3.2.1 and 3.3.2. Integrators and users are advised upgrade to 3.2.2 and 3.3.3 respectively. The mitigation against these vulnerabilities depends on the installation of the latest ModSecurity version (v2.9.6 / v3.0.8).

Weakness: CWE-116 (Improper Encoding or Escaping of Output), CWE-863 (Incorrect Authorization)

## Which versions are affected by CVE-2022-39956?

It affects 3 products.


Products: Debian Debian Linux, Fedoraproject Fedora, Owasp Owasp Modsecurity Core Rule Set.

## How do I fix CVE-2022-39956?

Upgrade to a fixed version.

## Is CVE-2022-39956 being exploited?

There is no known exploitation of CVE-2022-39956 in the wild and no public exploit code.

## Other vulnerabilities in Debian Debian Linux

- [CVE-2015-3306](https://insights.sbomify.com/CVE-2015-3306/): ProFTPD Improper Access Control (critical 10.0, exploited in the wild)
- [CVE-2025-49113](https://insights.sbomify.com/CVE-2025-49113/): RoundCube Webmail Deserialization of Untrusted Data (critical 9.9, exploited in the wild)
- [CVE-2026-24061](https://insights.sbomify.com/CVE-2026-24061/): GNU InetUtils Argument Injection (critical 9.8, exploited in the wild)
- [CVE-2025-39682](https://insights.sbomify.com/CVE-2025-39682/): Linux Kernel Improper Check for Unusual or Exceptional Conditions (critical 9.8, exploited in the wild)
- [CVE-2024-9680](https://insights.sbomify.com/CVE-2024-9680/): Mozilla Firefox Use-After-Free (critical 9.8, exploited in the wild)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2022-39956 and fix it if it is affected.

What it is: CVE-2022-39956 is a high-severity vulnerability in Debian Debian Linux, published on 20 Sep 2022. An attacker can exploit it over the internet without logging in, with no action from the victim.
Exploitation: There is no known exploitation of CVE-2022-39956 in the wild and no public exploit code.

Affected product: Debian Debian Linux. 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-2022-39956/ (Markdown: https://insights.sbomify.com/CVE-2022-39956/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2022-39956
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2022-39956
- OSV: https://osv.dev/vulnerability/CVE-2022-39956

---
From sbomify Insights: https://insights.sbomify.com/CVE-2022-39956/
Summaries are generated and may contain mistakes; the official description above is the record.