# CVE-2026-42344: FastGPT: DNS rebinding TOCTOU bypass in isInternalAddress allows SSRF on all protected endpoints

> Attackers can bypass internal address checks via DNS rebinding to perform Server-Side Request Forgery on protected endpoints in FastGPT.

- **Severity:** Medium 6.3 (`CVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:C/C:H/I:N/A:N`)
- **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:** 8 May 2026
- **Updated:** 11 May 2026
- **Also known as:** GHSA-cc8x-jrqv-hmwh

## What is CVE-2026-42344?

CVE-2026-42344 is a medium-severity server-side request forgery vulnerability in labring FastGPT, published on 8 May 2026. Any signed-in user can exploit it over the network, with no action from the victim.

### Official description

FastGPT is an AI Agent building platform. In versions 4.14.11 and prior, FastGPT's isInternalAddress() function in packages/service/common/system/utils.ts is vulnerable to DNS rebinding (TOCTOU — Time-of-Check to Time-of-Use). The function resolves the hostname via dns.resolve4()/dns.resolve6() and checks resolved IPs against private ranges, but the actual HTTP request happens in a separate call with a new DNS resolution, allowing the DNS record to change between validation and fetch. At time of publication, there are no publicly available patches.

Weakness: CWE-367 (Time-of-check Time-of-use (TOCTOU) Race Condition)

## Which versions are affected by CVE-2026-42344?


## How do I fix CVE-2026-42344?

No fix has been published for CVE-2026-42344 yet. Limit exposure of the affected software until one is available.

## Is CVE-2026-42344 being exploited?

It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-42344 exists.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-42344 and fix it if it is affected.

What it is: CVE-2026-42344 is a medium-severity server-side request forgery vulnerability in labring FastGPT, published on 8 May 2026. Any signed-in user can exploit it over the network, with no action from the victim.
Exploitation: It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-42344 exists.

Affected product: labring FastGPT. 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-2026-42344/ (Markdown: https://insights.sbomify.com/CVE-2026-42344/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-42344
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-42344
- OSV: https://osv.dev/vulnerability/CVE-2026-42344

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From sbomify Insights: https://insights.sbomify.com/CVE-2026-42344/
Summaries are generated and may contain mistakes; the official description above is the record.