# CVE-2026-39418: MaxKB: SSRF via sandbox network hook bypass

> Authenticated users can bypass sandbox network restrictions to access internal services via a socket flag bypass in MaxKB.

- **Severity:** Medium 5.0 (`CVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:U/C:L/I:L/A:L`)
- **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:** 14 Apr 2026
- **Updated:** 14 Apr 2026
- **Also known as:** GHSA-w9g4-q3gm-6q6w

## What is CVE-2026-39418?

CVE-2026-39418 is a medium-severity server-side request forgery vulnerability in 1Panel-dev MaxKB, published on 14 Apr 2026. Any signed-in user can exploit it over the network, with no action from the victim.

### Official description

MaxKB is an open-source AI assistant for enterprise. In versions 2.7.1 and below, sandbox network protection can be bypassed by using socket.sendto() with the MSG_FASTOPEN flag. This allows authenticated user with tool-editing permissions to reach internal services that are explicitly blocked by the sandbox's banned hosts configuration. MaxKB's sandbox uses LD_PRELOAD to hook the connect() function and block connections to banned IPs, but Linux's sendto() with the MSG_FASTOPEN flag can establish TCP connections directly through the kernel without ever calling connect(), completely bypassing the IP validation. Although sendto is listed in the syscall() wrapper, this is ineffective because glibc invokes the kernel syscall directly rather than routing through the hooked syscall() function. This issue has been fixed in version 2.8.0.

Weakness: CWE-918 (Server-Side Request Forgery)

## Which versions are affected by CVE-2026-39418?

It affects 1 product.


Products: Maxkb Maxkb.

## How do I fix CVE-2026-39418?

No fix has been published for CVE-2026-39418 yet. Limit exposure of the affected software until one is available.

## Is CVE-2026-39418 being exploited?

There is no known exploitation of CVE-2026-39418 in the wild and no public exploit code.

## Other vulnerabilities in 1Panel-dev MaxKB

- [CVE-2025-66419](https://insights.sbomify.com/CVE-2025-66419/): MaxKB vulnerable to privilege escalation through sandbox bypass (high 8.8)
- [CVE-2025-66446](https://insights.sbomify.com/CVE-2025-66446/): MaxKB has a Python sandbox LD_PRELOAD bypass (high 8.8)
- [CVE-2025-64511](https://insights.sbomify.com/CVE-2025-64511/): MaxKB has SSRF in sandbox (high 7.4)
- [CVE-2026-39422](https://insights.sbomify.com/CVE-2026-39422/): MaxKB has Stored XSS via ChatHeadersMiddleware (medium 6.9)
- [CVE-2026-39423](https://insights.sbomify.com/CVE-2026-39423/): Stored XSS via Eval Injection in EchartsRander Component (medium 6.9)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-39418 and fix it if it is affected.

What it is: CVE-2026-39418 is a medium-severity server-side request forgery vulnerability in 1Panel-dev MaxKB, published on 14 Apr 2026. Any signed-in user can exploit it over the network, with no action from the victim.
Exploitation: There is no known exploitation of CVE-2026-39418 in the wild and no public exploit code.

Affected product: 1Panel-dev MaxKB. 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-2026-39418/ (Markdown: https://insights.sbomify.com/CVE-2026-39418/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-39418
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-39418
- OSV: https://osv.dev/vulnerability/CVE-2026-39418

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From sbomify Insights: https://insights.sbomify.com/CVE-2026-39418/
Summaries are generated and may contain mistakes; the official description above is the record.