# CVE-2026-27642: free5GC has Improper Input Validation in UDM UEAU Service

> Remote attackers can inject control characters into the UDM UEAU service to trigger errors that expose system details, aiding service fingerprinting.

- **Severity:** Medium 6.6 (`CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:H/VI:N/VA:N/SC:N/SI:N/SA:N/E:U`)
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** No
- **Published:** 24 Feb 2026
- **Updated:** 26 Feb 2026
- **Also known as:** GHSA-h4wg-rp7m-8xx4

## What is CVE-2026-27642?

CVE-2026-27642 is a medium-severity vulnerability in free5gc udm, published on 24 Feb 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.

### Official description

free5gc UDM provides Unified Data Management (UDM) for free5GC, an open-source project for 5th generation (5G) mobile core networks. In versions up to and including 1.4.1, remote attackers can inject control characters (e.g., %00) into the supi parameter, triggering internal URL parsing errors (net/url: invalid control character). This exposes system-level error details and can be used for service fingerprinting. All deployments of free5GC using the UDM Nudm_UEAU service may be affected. free5gc/udm pull request 75 contains a fix for the issue. No direct workaround is available at the application level. Applying the official patch is recommended.

Weakness: CWE-20 (Improper Input Validation)

## Which versions are affected by CVE-2026-27642?

It affects 1 product.


Products: Free5gc Udm.

## How do I fix CVE-2026-27642?

No fix has been published for CVE-2026-27642 yet. Limit exposure of the affected software until one is available.

## Is CVE-2026-27642 being exploited?

There is no known exploitation of CVE-2026-27642 in the wild and no public exploit code.

## Other vulnerabilities in free5gc udm

- [CVE-2026-33064](https://insights.sbomify.com/CVE-2026-33064/): free5GC UDM DataChangeNotification Procedure Panic Due to Nil Pointer Dereference (high 8.7)
- [CVE-2026-33191](https://insights.sbomify.com/CVE-2026-33191/): free5GC UDM vulnerable to null byte injection in URL path parameters causing 500 Internal Server Error (high 8.7)
- [CVE-2026-33192](https://insights.sbomify.com/CVE-2026-33192/): free5GC UDM incorrectly returns 500 for empty supi path parameter in PATCH sdm-subscriptions reques (high 8.7)
- [CVE-2023-46324](https://insights.sbomify.com/CVE-2023-46324/): free5GC udm vulnerable to Invalid Curve Attack (high 7.5)
- [CVE-2026-33065](https://insights.sbomify.com/CVE-2026-33065/): free5GC UDM incorrectly returns 500 for empty supi path parameter in DELETE sdm-subscriptions request (medium 6.9)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-27642 and fix it if it is affected.

What it is: CVE-2026-27642 is a medium-severity vulnerability in free5gc udm, published on 24 Feb 2026. 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-2026-27642 in the wild and no public exploit code.

Affected product: free5gc udm. 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-2026-27642/ (Markdown: https://insights.sbomify.com/CVE-2026-27642/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-27642
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-27642
- OSV: https://osv.dev/vulnerability/CVE-2026-27642

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-27642/
Summaries are generated and may contain mistakes; the official description above is the record.