# CVE-2025-6599: Denial of service in DX3301-T0 firmware

> Attackers can cause denial of service on the web management interface via Slowloris attacks, requiring firmware upgrades.

- **Severity:** Medium 5.3 (`CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L`)
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** No
- **Published:** 18 Nov 2025
- **Updated:** 18 Nov 2025
- **Also known as:** GHSA-r99r-5wp8-8w99

## What is CVE-2025-6599?

CVE-2025-6599 is a medium-severity denial of service vulnerability in Zyxel DX3301-T0 firmware, published on 18 Nov 2025. An attacker can exploit it over the internet without logging in, with no action from the victim.

### Official description

An uncontrolled resource consumption vulnerability in the web server of Zyxel DX3301-T0 firmware version 5.50(ABVY.6.3)C0 and earlier could allow an attacker to perform Slowloris‑style denial‑of‑service (DoS) attacks. Such attacks may temporarily block legitimate HTTP requests and partially disrupt access to the web management interface, while other networking services remain unaffected.

Weakness: CWE-400 (Uncontrolled Resource Consumption)

## Which versions are affected by CVE-2025-6599?

It affects 66 products.


Products: Zyxel Ax7501-B0 Firmware, Zyxel Ax7501-B1 Firmware, Zyxel Dm4200-B0 Firmware, Zyxel Dx3300-T0 Firmware, Zyxel Dx3300-T1 Firmware, Zyxel Dx3301-T0 Firmware, Zyxel Dx4510-B1 Firmware, Zyxel Dx5401-B0 Firmware, Zyxel Dx5401-B1 Firmware, Zyxel Ee3301-00 Firmware, Zyxel Ee5301-00 Firmware, Zyxel Ee6510-10 Firmware, Zyxel Emg3525-T50b Firmware, Zyxel Emg5523-T50b Firmware, Zyxel Emg5723-T50k Firmware, Zyxel Emg6726-B10a Firmware, Zyxel Ex3300-T0 Firmware, Zyxel Ex3300-T1 Firmware, Zyxel Ex3301-T0 Firmware, Zyxel Ex3500-T0 Firmware and 46 more.

## How do I fix CVE-2025-6599?

No fix has been published for CVE-2025-6599 yet. Limit exposure of the affected software until one is available.

## Is CVE-2025-6599 being exploited?

There is no known exploitation of CVE-2025-6599 in the wild and no public exploit code.

## Other vulnerabilities in Zyxel DX3301-T0 firmware

- [CVE-2025-8693](https://insights.sbomify.com/CVE-2025-8693/): Command injection in DX3300-T0 firmware (high 8.8)
- [CVE-2022-26413](https://insights.sbomify.com/CVE-2022-26413/): Command injection in VMG3312-T20A firmware (high 8.0)
- [CVE-2024-8748](https://insights.sbomify.com/CVE-2024-8748/): Memory corruption in VMG8825-T50K firmware (high 7.5)
- [CVE-2024-5412](https://insights.sbomify.com/CVE-2024-5412/): Memory corruption in VMG8825-T50K firmware (high 7.5)
- [CVE-2024-12009](https://insights.sbomify.com/CVE-2024-12009/): Command injection in EX5601-T1 firmware (high 7.2)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2025-6599 and fix it if it is affected.

What it is: CVE-2025-6599 is a medium-severity denial of service vulnerability in Zyxel DX3301-T0 firmware, published on 18 Nov 2025. 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-2025-6599 in the wild and no public exploit code.

Affected product: Zyxel DX3301-T0 firmware. 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-2025-6599/ (Markdown: https://insights.sbomify.com/CVE-2025-6599/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2025-6599
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2025-6599
- OSV: https://osv.dev/vulnerability/CVE-2025-6599

---
From sbomify Insights: https://insights.sbomify.com/CVE-2025-6599/
Summaries are generated and may contain mistakes; the official description above is the record.