# CVE-2026-85738: TREK: SSRF Guard Bypass via IPv6 Transition Addresses (NAT64/6to4)

> Authenticated users can bypass SSRF protections using IPv6 transition addresses to access internal services or cloud metadata in TREK.

- **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:** 24 Sep 2026
- **Updated:** 28 Sep 2026
- **Also known as:** GHSA-9hpq-mrpx-mcxg

## What is CVE-2026-85738?

CVE-2026-85738 is a medium-severity server-side request forgery vulnerability in liketrek TREK, published on 24 Sep 2026. Any signed-in user can exploit it over the network, with no action from the victim.

### Official description

TREK is a collaborative travel planner. Prior to 3.4.0, the checkSsrf logic in server/src/utils/ssrfGuard.ts does not recognize NAT64, 6to4, or Teredo IPv6 transition addresses that encode an IPv4 destination. An authenticated user who controls a DNS record can supply a URL whose AAAA result is a transition address embedding a private, loopback, or link-local IPv4 target, and isAlwaysBlocked and isPrivateNetwork classify the address as allowed. In a deployment that routes the applicable transition format, user-facing imports, webhooks, integrations, or plugin egress can reach internal services or cloud metadata and expose returned information. This issue is fixed in version 3.4.0.

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

## Which versions are affected by CVE-2026-85738?


## How do I fix CVE-2026-85738?

No fix has been published for CVE-2026-85738 yet. Limit exposure of the affected software until one is available.

## Is CVE-2026-85738 being exploited?

It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-85738 exists.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-85738 and fix it if it is affected.

What it is: CVE-2026-85738 is a medium-severity server-side request forgery vulnerability in liketrek TREK, published on 24 Sep 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-2026-85738 exists.

Affected product: liketrek TREK. 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-2026-85738/ (Markdown: https://insights.sbomify.com/CVE-2026-85738/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-85738
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-85738
- OSV: https://osv.dev/vulnerability/CVE-2026-85738

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-85738/
Summaries are generated and may contain mistakes; the official description above is the record.