# CVE-2026-0400: Denial of service in SonicOS

> A post-authentication format string vulnerability in SonicOS allows remote attackers to crash the firewall, requiring vendor patches.

- **Severity:** Medium 4.9 (`CVSS:3.1/AV:N/AC:L/PR:H/UI:N/S:U/C:N/I:N/A:H`)
- **Exploited in the wild:** Not known
- **Login needed:** An administrator
- **Attackable:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** No
- **Published:** 24 Feb 2026
- **Updated:** 24 Feb 2026
- **Also known as:** GHSA-3q93-28v9-5x6v

## What is CVE-2026-0400?

CVE-2026-0400 is a medium-severity denial of service vulnerability in Sonicwall Sonicos, published on 24 Feb 2026. An attacker needs administrator access to exploit it, with no action from the victim.

### Official description

A post-authentication Format String vulnerability in SonicOS allows a remote attacker to crash a firewall.

Weakness: CWE-134 (Use of Externally-Controlled Format String)

## Which versions are affected by CVE-2026-0400?

It affects 1 product.


Products: Sonicwall Sonicos.

## How do I fix CVE-2026-0400?

No fix has been published for CVE-2026-0400 yet. Limit exposure of the affected software until one is available.

## Is CVE-2026-0400 being exploited?

There is no known exploitation of CVE-2026-0400 in the wild and no public exploit code.

## Other vulnerabilities in Sonicwall Sonicos

- [CVE-2020-5135](https://insights.sbomify.com/CVE-2020-5135/): SonicWall SonicOS Buffer Overflow (critical 9.8, exploited in the wild)
- [CVE-2024-40766](https://insights.sbomify.com/CVE-2024-40766/): SonicWall SonicOS Improper Access Control (critical 9.3, exploited in the wild)
- [CVE-2024-53704](https://insights.sbomify.com/CVE-2024-53704/): SonicWall SonicOS SSLVPN Improper Authentication (high 8.2, exploited in the wild)
- [CVE-2025-40600](https://insights.sbomify.com/CVE-2025-40600/): Denial of service in SonicOS (critical 9.8)
- [CVE-2024-22394](https://insights.sbomify.com/CVE-2024-22394/): Auth bypass in SonicOS (critical 9.8)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-0400 and fix it if it is affected.

What it is: CVE-2026-0400 is a medium-severity denial of service vulnerability in Sonicwall Sonicos, published on 24 Feb 2026. An attacker needs administrator access to exploit it, with no action from the victim.
Exploitation: There is no known exploitation of CVE-2026-0400 in the wild and no public exploit code.

Affected product: Sonicwall Sonicos. 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-2026-0400/ (Markdown: https://insights.sbomify.com/CVE-2026-0400/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-0400
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-0400
- OSV: https://osv.dev/vulnerability/CVE-2026-0400

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-0400/
Summaries are generated and may contain mistakes; the official description above is the record.