# CVE-2021-35300: Open redirect in n/a

> Remote attackers can manipulate users into visiting malicious pages via content spoofing in the 404 error page of Zammad.

- **Severity:** Medium 4.3 (`CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:N/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:** 28 Jun 2021
- **Updated:** 4 Aug 2024
- **Also known as:** GHSA-r2cr-p267-3cp7

## What is CVE-2021-35300?

CVE-2021-35300 is a medium-severity vulnerability in Zammad Zammad, published on 28 Jun 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

Text injection/Content Spoofing in 404 page in Zammad 1.0.x up to 4.0.0 could allow remote attackers to manipulate users into visiting the attackers' page.

Weakness: CWE-1021 (Improper Restriction of Rendered UI Layers or Frames)

## Which versions are affected by CVE-2021-35300?

It affects 1 product.


Products: Zammad Zammad.

## How do I fix CVE-2021-35300?

No fix has been published for CVE-2021-35300 yet. Limit exposure of the affected software until one is available.

## Is CVE-2021-35300 being exploited?

There is no known exploitation of CVE-2021-35300 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-2021-35300 and fix it if it is affected.

What it is: CVE-2021-35300 is a medium-severity vulnerability in Zammad Zammad, published on 28 Jun 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-2021-35300 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-2021-35300/ (Markdown: https://insights.sbomify.com/CVE-2021-35300/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2021-35300
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2021-35300
- OSV: https://osv.dev/vulnerability/CVE-2021-35300

---
From sbomify Insights: https://insights.sbomify.com/CVE-2021-35300/
Summaries are generated and may contain mistakes; the official description above is the record.