Executive brief
Open5GS is an open-source implementation of 5G core network infrastructure. A flaw in the PFCP (Packet Forwarding Control Protocol) message handler can cause the service to crash when processing maliciously crafted or malformed PFCP messages, disrupting 5G network operations and connectivity.
Technical details
The vulnerability is an assertion failure (denial of service) in the PFCP Message Handler component (lib/pfcp/handler.c) affecting Open5GS up to version 2.7.7. The root cause is insufficient validation of the Outer Header Creation (OHC) IE (Information Element) in Create/Update FAR (Forwarding Action Rule) PFCP messages. Specifically, truncated or unsupported GTP-U/IPv6 IEs could be partially copied into a zero-initialized FAR structure, leaving incompletely initialized fields that later trigger an "Unknown family" assertion on subsequent requests. The attack is network-accessible and requires no authentication, as PFCP is a control-plane protocol exposed to the network. An attacker can craft malformed PFCP messages to crash the UPF (User Plane Function) or MME components. The fix (commit 028e1dbb5e3271035ccee906ef417a97fc523f71) validates OHC before copying and rejects invalid/unsupported variants.
Affected products
- Open5GS Open5GS up to 2.7.7
Timeline
- 2026-09-15: disclosed
- 2026-08-06: patched: Fix commit 028e1dbb5e3271035ccee906ef417a97fc523f71