UBUNTU-CVE-2026-64545: Null Pointer Dereference
In the Linux kernel, the following vulnerability has been resolved: net, bpf: check master for NULL in xdpmasterredirect() xdpmasterredirect() dereferences the result of netdevmasterupperdevgetrcu() without a NULL check, but that helper returns NULL when the receiving device has no upper-master adjacency. The reach guard only checks netifisbondslave(). On bond slave release bondupperdevunlink() drops the upper-master adjacency before clearing IFFSLAVE, so an XDPTX reaching xdpmasterredirect() in that window still passes netifisbondslave() while master is already NULL, and faults on master->flags at offset 0xb0: BUG: kernel NULL pointer dereference, address: 00000000000000b0 RIP: 0010:xdpmasterredirect (net/core/filter.c:4432) Call Trace: xdpmasterredirect (net/core/filter.c:4432) bpfprogrungenericxdp (include/net/xdp.h:700) doxdpgeneric (net/core/dev.c:5608) netifreceiveskbonecore (net/core/dev.c:6204) processbacklog (net/core/dev.c:6319) napipoll (net/core/dev.c:7729) netrxaction (net/core/dev.c:7792) handlesoftirqs (kernel/softirq.c:622) devqueuexmit (include/linux/bottomhalf.h:33) packetsendmsg (net/packet/afpacket.c:3082) syssendto (net/socket.c:2252) Kernel panic - not syncing: Fatal exception in interrupt The missing check dates back to the original code; commit 1921f91298d1 ("net, bpf: fix null-ptr-deref in xdpmasterredirect() for down master") later added the master->flags read where the fault now lands but kept the unconditional deref. Check master for NULL before use; a NULL master is treated the same as one that is not up.
Affected Software
Remediation
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In xdp_master_redirect(), check whether the master returned by netdev_master_upper_dev_get_rcu() is NULL before dereferencing it; treat a NULL master the same as a master that is not up.
Event History
Frequently Asked Questions
Which systems are exposed to the crash condition?
Systems using a bonded network interface can be exposed when a bond slave is released while an XDP_TX path reaches the affected redirect logic. The failure window exists after the upper-master relationship is removed but before the slave flag is cleared.
What is the operational impact if the issue is triggered?
The kernel can dereference a NULL master device pointer in xdp_master_redirect(), causing a kernel NULL pointer dereference. The reported outcome is a fault in the networking receive path, resulting in a denial of service.
How can I recognize that this vulnerability has been triggered?
Look for a kernel NULL pointer dereference at address 0x00000000000000b0 with xdp_master_redirect in the stack trace. The trace may include bpf_prog_run_generic_xdp, do_xdp_generic, and network receive-path functions such as __netif_receive_skb_one_core and net_rx_action.