# CVE-2021-42084: Denial of service in n/a

> An authenticated agent can trigger an endless loop via crafted requests, causing a denial of service in Zammad.

- **Severity:** Medium 6.5 (`CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H`)
- **Exploited in the wild:** Not known
- **Login needed:** Any signed-in user
- **Attackable:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** No
- **Published:** 7 Oct 2021
- **Updated:** 4 Aug 2024
- **Also known as:** GHSA-2wm3-m74f-6p2x

## What is CVE-2021-42084?

CVE-2021-42084 is a medium-severity denial of service vulnerability in Zammad Zammad, published on 7 Oct 2021. Any signed-in user can exploit it over the network, with no action from the victim.

### Official description

An issue was discovered in Zammad before 4.1.1. An attacker with valid agent credentials may send a series of crafted requests that cause an endless loop and thus cause denial of service.

Weakness: CWE-835 (Loop with Unreachable Exit Condition)

## Which versions are affected by CVE-2021-42084?

It affects 1 product.


Products: Zammad Zammad.

## How do I fix CVE-2021-42084?

No fix has been published for CVE-2021-42084 yet. Limit exposure of the affected software until one is available.

## Is CVE-2021-42084 being exploited?

There is no known exploitation of CVE-2021-42084 in the wild and no public exploit code.

## Other vulnerabilities in Zammad Zammad

- [CVE-2026-102489](https://insights.sbomify.com/CVE-2026-102489/): Zammad GmbH Zammad Session Fixation (high 8.7, exploited in the wild)
- [CVE-2026-102490](https://insights.sbomify.com/CVE-2026-102490/): Zammad GmbH Zammad Improper Privilege Management (high 8.5, exploited in the wild)
- [CVE-2022-48021](https://insights.sbomify.com/CVE-2022-48021/): Code injection in n/a (critical 9.8)
- [CVE-2022-35490](https://insights.sbomify.com/CVE-2022-35490/): Security feature bypass in n/a (critical 9.8)
- [CVE-2021-42090](https://insights.sbomify.com/CVE-2021-42090/): Deserialization in n/a (critical 9.8)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2021-42084 and fix it if it is affected.

What it is: CVE-2021-42084 is a medium-severity denial of service vulnerability in Zammad Zammad, published on 7 Oct 2021. Any signed-in user can exploit it over the network, with no action from the victim.
Exploitation: There is no known exploitation of CVE-2021-42084 in the wild and no public exploit code.

Affected product: Zammad Zammad. 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-2021-42084/ (Markdown: https://insights.sbomify.com/CVE-2021-42084/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2021-42084
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2021-42084
- OSV: https://osv.dev/vulnerability/CVE-2021-42084

---
From sbomify Insights: https://insights.sbomify.com/CVE-2021-42084/
Summaries are generated and may contain mistakes; the official description above is the record.