# CVE-2026-55784: free5GC AUSF authentication contexts can be overwritten by concurrent requests for the same SUPI

> Concurrent authentication requests for the same subscriber overwrite shared state, causing authentication failures and denial of service in free5GC.

- **Severity:** High 7.5 (`CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H`)
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** Yes
- **Published:** 28 Aug 2026
- **Updated:** 1 Sep 2026
- **Also known as:** GHSA-334q-h5g3-fpxv, GO-2026-6326

## What is CVE-2026-55784?

CVE-2026-55784 is a high-severity vulnerability in free5gc, published on 28 Aug 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.

### Official description

free5GC is an open-source implementation of the 5G core network. In version 1.4.4 and earlier, the AUSF component stores per-subscriber authentication state in a global sync.Map named AUSFContext.UePool in internal/context/context.go, keyed only by SUPI. Every request handled by internal/sbi/processor/ue_authentication.go creates an AusfUeContext, and AddAusfUeContextToPool executes ausfContext.UePool.Store(ausfUeContext.Supi, ausfUeContext), unconditionally replacing the active context for that SUPI. An attacker with access to the AUSF SBI/N12 interface can send concurrent POST /nausf-auth/v1/ue-authentications requests for the same target SUPI, causing all attempts to share one logical authentication context URL while K_aut, XRES, and EapID are repeatedly overwritten. A valid EAP-AKA' response for an earlier challenge is then checked against the latest context, causing AT_MAC verification to fail and denying authentication to the selected subscriber while the request flood continues. No fixed version is available as of this review.

Weakness: CWE-362 (Concurrent Execution using Shared Resource with Improper Synchronization)

## Which versions are affected by CVE-2026-55784?

3 open source packages ship an affected version, including github.com/free5gc/ausf.


| Package | Ecosystem | Affected | Fixed in |
| --- | --- | --- | --- |
| `github.com/free5gc/ausf` | Go | All versions | None |
| `github.com/free5gc/ausf` | Go | All versions to 1.4.4 | None |
| `github.com/free5gc/ausf` | Go | All versions to 1.4.4 | None |

## How do I fix CVE-2026-55784?

No fix published yet.

## Is CVE-2026-55784 being exploited?

It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-55784 exists.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-55784 and fix it if it is affected.

What it is: CVE-2026-55784 is a high-severity vulnerability in free5gc, published on 28 Aug 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.
Exploitation: It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-55784 exists.

Affected packages and fixed versions:
- github.com/free5gc/ausf (Go): affected all versions; no fix listed
- github.com/free5gc/ausf (Go): affected all versions up to 1.4.4; no fix listed
- github.com/free5gc/ausf (Go): affected all versions up to 1.4.4; no fix listed

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-2026-55784/ (Markdown: https://insights.sbomify.com/CVE-2026-55784/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-55784
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-55784
- OSV: https://osv.dev/vulnerability/CVE-2026-55784

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-55784/
Summaries are generated and may contain mistakes; the official description above is the record.