free5GC UDM DataChangeNotification Procedure Panic Due to Nil Pointer Dereference
**Impact** This is a NULL Pointer Dereference vulnerability leading to Denial of Service. - **Security Impact**: A remote attacker can cause the UDM service to panic and crash by sending a crafted POST request to the `/sdm-subscriptions` endpoint with a malformed URL path containing path traversal sequences (`../`) and a large JSON payload. The `DataChangeNotificationProcedure` function in `notifier.go` attempts to access a nil pointer without proper validation, causing a complete service crash with "runtime error: invalid memory address or nil pointer dereference". - **Functional Impact**: The service crashes completely, requiring manual restart. All UDM functionality is disrupted until recovery. - **Affected Parties**: All deployments of free5GC v4.0.1 using the UDM HTTP callback functionality. **Patches** Yes, the issue has been patched. The fix is implemented in PR free5gc/udm#78. Users should upgrade to the next release of free5GC that includes this commit. **Workarounds** There is no direct workaround at the application level. The recommendation is to apply the provided patch or implement API gateway-level filtering to block requests containing path traversal sequences.
02 / AFFECTED SOFTWARE
Affected packages
16 explicit affected versions
03 / CONNECTIONS
Connected vulnerabilities
04 / EVIDENCE
Source records
Free5GC is an open-source Linux Foundation project for 5th generation (5G) mobile core networks. Versions prior to 1.4.2 are vulnerable to procedure panic caused by Nil Pointer Dereference in the /sdm-subscriptions endpoint. A remote attacker can cause the UDM service to panic and crash by sending a crafted POST request to the /sdm-subscriptions endpoint with a malformed URL path containing path traversal sequences (../) and a large JSON payload. The DataChangeNotificationProcedure function in notifier.go attempts to access a nil pointer without proper validation, causing a complete service crash with "runtime error: invalid memory address or nil pointer dereference". Exploitation would result in UDM functionality disruption until recovery by restart. This issue has been fixed in version 1.4.2.
**Impact** This is a NULL Pointer Dereference vulnerability leading to Denial of Service. - **Security Impact**: A remote attacker can cause the UDM service to panic and crash by sending a crafted POST request to the `/sdm-subscriptions` endpoint with a malformed URL path containing path traversal sequences (`../`) and a large JSON payload. The `DataChangeNotificationProcedure` function in `notifier.go` attempts to access a nil pointer without proper validation, causing a complete service crash with "runtime error: invalid memory address or nil pointer dereference". - **Functional Impact**: The service crashes completely, requiring manual restart. All UDM functionality is disrupted until recovery. - **Affected Parties**: All deployments of free5GC v4.0.1 using the UDM HTTP callback functionality. **Patches** Yes, the issue has been patched. The fix is implemented in PR free5gc/udm#78. Users should upgrade to the next release of free5GC that includes this commit. **Workarounds** There is no direct workaround at the application level. The recommendation is to apply the provided patch or implement API gateway-level filtering to block requests containing path traversal sequences.
free5GC UDM DataChangeNotification Procedure Panic Due to Nil Pointer Dereference in github.com/free5gc/udm
05 / REFERENCES
Further evidence
- https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/33xxx/CVE-2026-33064.json
- https://github.com/free5gc/free5gc/issues/781
- https://github.com/free5gc/free5gc/security/advisories/GHSA-7g27-v5wj-jr75
- https://github.com/free5gc/udm/commit/65d7070f4bfd016864cbbaefbd506bbc85d2fa92
- https://github.com/free5gc/udm/pull/78
- https://nvd.nist.gov/vuln/detail/CVE-2026-33064
- https://github.com/free5gc/udm