CVE-2026-44322 Overview
CVE-2026-44322 is a nil-pointer dereference vulnerability in free5GC, an open-source implementation of the 5G core network. The flaw affects the Network Exposure Function (NEF) PATCH handler for /3gpp-pfd-management/v1/{afId}/transactions/{transId}/applications/{appId}. When the upstream Unified Data Repository (UDR) call fails and the consumer wrapper returns a non-nil error alongside a nil *ProblemDetails, the handler panics. Gin recovery converts the panic into an HTTP 500 response, allowing unauthenticated network attackers to trigger denial of service against the NEF component. The vulnerability is fixed in free5GC version 4.2.2.
Critical Impact
A single PATCH request to the affected NEF endpoint causes the handler to panic and return HTTP 500 whenever UDR access is failing, disrupting Packet Flow Description (PFD) management operations.
Affected Products
- free5GC versions prior to 4.2.2
- free5GC NEF (Network Exposure Function) component
- free5GC nef module PFD management handler
Discovery Timeline
- 2026-05-27 - CVE-2026-44322 published to NVD
- 2026-05-27 - Last updated in NVD database
Technical Details for CVE-2026-44322
Vulnerability Analysis
The vulnerability resides in the NEF PATCH handler responsible for PFD management transactions. The handler invokes a consumer wrapper that calls the UDR. When the UDR call fails, the wrapper can return a non-nil err value together with a nil *ProblemDetails pointer. The handler's errPfdData != nil branch correctly constructs its own local problemDetailsErr structure. However, immediately after constructing this local value, the code dereferences the original problemDetails.Cause field instead of the locally built object. Because problemDetails is nil in this code path, the dereference triggers a runtime panic. Gin's recovery middleware intercepts the panic and converts it into an HTTP 500 response.
Root Cause
The root cause is improper null-pointer handling [CWE-476] in the error path of the PFD management PATCH handler. Two distinct error-representation objects exist in the same scope: the locally constructed problemDetailsErr and the upstream problemDetails. The handler reads Cause from the wrong variable, accessing a nil pointer whenever the UDR consumer path produces this specific error tuple.
Attack Vector
The vulnerability is exploitable over the network without authentication or user interaction. An attacker capable of reaching the NEF management API can send a single PATCH request to the PFD management endpoint. When the backing UDR is unavailable or returning errors, every such request triggers the panic. This produces a denial-of-service condition affecting PFD management functionality within the 5G core network.
No verified exploit code is publicly available. See the GitHub Security Advisory and the GitHub Issue Report for technical details.
Detection Methods for CVE-2026-44322
Indicators of Compromise
- HTTP 500 responses returned by NEF endpoints under the /3gpp-pfd-management/v1/ path during periods of UDR instability.
- Gin recovery middleware panic traces in NEF logs referencing the PFD management handler and nil-pointer dereference.
- Repeated PATCH requests targeting /3gpp-pfd-management/v1/{afId}/transactions/{transId}/applications/{appId} from a single source.
Detection Strategies
- Inspect NEF application logs for Go runtime panic stack traces containing nil pointer dereference paired with PFD management handler frames.
- Correlate UDR connectivity failures with spikes in NEF 5xx responses on the PFD management route.
- Alert on unexpected PATCH requests against PFD management endpoints from untrusted network segments.
Monitoring Recommendations
- Track NEF availability metrics and HTTP 5xx error ratios for PFD management endpoints.
- Monitor UDR service health and alert when UDR errors coincide with NEF panic events.
- Capture and retain Gin recovery logs for forensic review of repeated panic conditions.
How to Mitigate CVE-2026-44322
Immediate Actions Required
- Upgrade free5GC to version 4.2.2 or later, which contains the fix for the nil-pointer dereference.
- Restrict network access to the NEF PFD management API to trusted Application Function (AF) clients only.
- Validate UDR service health and stability to reduce the frequency of the triggering error path.
Patch Information
The fix is included in free5GC 4.2.2. The upstream code change is available in the free5GC nef commit 72a47f3 and the corresponding Pull Request #22. The patch corrects the error branch so that it reads from the locally constructed problemDetailsErr rather than dereferencing the nil upstream problemDetails.
Workarounds
- Place the NEF behind a reverse proxy or API gateway that enforces authentication and rate limiting on PFD management routes.
- Apply network ACLs restricting PATCH access to the affected endpoint to known AF source addresses.
- Implement health-check based circuit breaking between NEF and UDR to fail fast before invoking the vulnerable handler path.
# Upgrade free5GC to the patched release
git clone https://github.com/free5gc/free5gc.git
cd free5gc
git checkout v4.2.2
make all
Disclaimer: This content was generated using AI. While we strive for accuracy, please verify critical information with official sources.
