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.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Over the internet
- Victim action needed
- Not needed
- Fix
- Available
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
Which versions are affected by CVE-2026-55784?
3 open source packages ship an affected version, including github.com/free5gc/ausf.
| Package | 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.
Sources
Also known as GHSA-334q-h5g3-fpxv, GO-2026-6326.