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CVE-2026-64545
net, bpf: check master for NULL in xdp_master_redirect()
Published 2026-07-27 (3 months ago) by the Linux kernel CNA. Subsystem net/core. Debian urgency: not yet assigned.
What to do, per Debian release
Debian's own status for CVE-2026-64545 in every release this site tracks, and what each one means in practice. Every status below is the one the Debian Security Team publishes for this CVE. source
| Release | Status | Version | What this means |
|---|---|---|---|
| Debian 12bookworm | fixedDLA-4720-1 · 2026-08-05 · text | 6.1.180-1 | Update the kernel and reboot. DLA-4720-1 shipped the fix on 2026-08-05, in 6.1.180-1. A running kernel keeps the old code until the machine restarts. |
| Debian 13trixie | fixedDSA-6405-1 · 2026-07-31 · text | 6.12.100-1 | Update the kernel and reboot. DSA-6405-1 shipped the fix on 2026-07-31, in 6.12.100-1. A running kernel keeps the old code until the machine restarts. |
| Debian 14forky | fixed | 7.1.5-1 | Update the kernel and reboot. Fixed in 7.1.5-1. A running kernel keeps the old code until the machine restarts. |
| Debian unstablesid | fixed | 7.1.5-1 | Update the kernel and reboot. Fixed in 7.1.5-1. A running kernel keeps the old code until the machine restarts. |
| Debian 12bookworm · linux-6.12 | fixedDLA-4724-1 · 2026-08-07 · text | 6.12.100-1~deb12u1 | Update the kernel and reboot. DLA-4724-1 shipped the fix on 2026-08-07, in 6.12.100-1~deb12u1. A running kernel keeps the old code until the machine restarts. |
The vulnerability
What the bug is
xdp_master_redirect() dereferences the result of netdev_master_upper_dev_get_rcu() without a NULL check, but that helper returns NULL when the receiving device has no upper-master adjacency. The reach guard only checks netif_is_bond_slave(). On bond slave release bond_upper_dev_unlink() drops the upper-master adjacency before clearing IFF_SLAVE, so an XDP_TX reaching xdp_master_redirect() in that window still passes netif_is_bond_slave() while master is already NULL, and faults on master->flags at offset 0xb0: BUG: kernel NULL pointer dereference, address: 00000000000000b0 RIP: 0010:xdp_master_redirect (net/core/filter.c:4432) Call Trace: xdp_master_redirect (net/core/filter.c:4432) bpf_prog_run_generic_xdp (include/net/xdp.h:700) do_xdp_generic (net/core/dev.c:5608) __netif_receive_skb_one_core (net/core/dev.c:6204) process_backlog (net/core/dev.c:6319) __napi_poll (net/core/dev.c:7729) net_rx_action (net/core/dev.c:7792) handle_softirqs (kernel/softirq.c:622) __dev_queue_xmit (include/linux/bottom_half.h:33) packet_sendmsg (net/packet/af_packet.c:3082) __sys_sendto (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 xdp_master_redirect() 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.
Where it lives
The fix touches these files. If the subsystem is one you do not use, the practical exposure is lower, though the package is still the vulnerable one.
net/core/filter.c
- What this is
- BPF [GENERAL] (Safe Dynamic Programs and Tools)MAINTAINERS section matched on net/core/filter.c · bpf@vger.kernel.org · Supported
Show whether Debian builds this, per release
Debian builds this code. Every release below compiles the affected file into the kernels it ships.
- bookworm, trixie, forky, sid, bookworm · linux-6.12y
- y
- built into the kernel image on every flavour - only a patch removes it
From the configuration Debian publishes for every kernel flavour it builds. It covers only the architectures Debian ships a linux-config package for, and nothing about a kernel you built yourself. Debian's own status above stays authoritative about the source package.MAINTAINERS Debian linux-config packages
Signals
- Published
- 2026-07-27 (3 months ago)source
- CVSS
- 7.5 high
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:Hsource recompute it - Attack vector
- network (AV:N)source
- EPSS
- 0.58%, higher than 46.5% of all CVEssource
- CISA KEV
- not listedthe KEV catalogue
- Debian urgency
- not yet assignedsource
- Subsystem
- net/core
Upstream fixes
The versions the CNA records as introducing and fixing this, and the commit for each. source
| Introduced | Fixed in | Commit |
|---|---|---|
| 5.15 | 5.15.212 | c99ca049e910 |
| 5.15 | 6.1.178 | e2a564412331 |
| 5.15 | 6.6.145 | 3876318ea54e |
| 5.15 | 6.12.97 | 4edbcacca09f |
| 5.15 | 6.18.40 | 03b743586a24 |
| 5.15 | 7.1.5 | 89c103d702b2 |
| 5.15 | 7.2 | e82d8cc4321c |
Debian advisories
| Advisory | Date | Shipped to | Debian |
|---|---|---|---|
| DLA-4724-1 | 2026-08-07 | bookworm 6.12.100-1~deb12u1 | tracker |
| DLA-4723-1 | 2026-08-07 | bullseye 6.1.180-1~deb11u1 | tracker |
| DLA-4720-1 | 2026-08-05 | bookworm 6.1.180-1 | tracker |
| DSA-6405-1 | 2026-07-31 | trixie 6.12.100-1 | tracker |
Why the CNA scored it this way
Quoted from the kernel CNA's own scoring file, word for word. A highlighted metric carries the most severe value CVSS v3.1 defines for it, which is what pushes the score up. source
- AV:NAttack vector, network
- The faulting path is the XDP receive hook — packets arriving on a bond slave drive `bpf_prog_run_xdp`/`do_xdp_generic` → `xdp_master_redirect()`, so a remote attacker sending traffic to a bonded interface running an XDP_TX program (XDP load balancers/DDoS scrubbers on bonded uplinks are a mainstream deployment) supplies the triggering packets with no local access.
- AC:LAttack complexity, low
- The attacker controls the packet side of the race and can sustain line-rate traffic so the multi-microsecond window between adjacency teardown and `IFF_SLAVE` clearing is hit essentially deterministically; where the attacker also holds the network configuration side (container/netns with bond and XDP control) both sides of the race are attacker-driven, which the kernel guidance classes as Low.
- PR:NPrivileges required, none
- No credentials or authentication are needed to send frames to a bonded interface, and the fault occurs in softirq during receive processing before any socket, filesystem, or user-level authorization is consulted — matching the PR:N treatment of the sibling fix CVE-2026-53069 in this same function.
- UI:NUser interaction, none
- No victim action is required; the slave-release window is reached by routine and externally-induced events (bond reconfiguration, `bond_enslave` rollback, NIC hotplug/`NETDEV_UNREGISTER`), and the attacker need only keep traffic flowing.
- S:UScope, unchanged
- The NULL dereference and its consequences are confined to the kernel's own security authority; no hypervisor, IOMMU, or sandbox boundary is crossed.
- C:NConfidentiality impact, none
- The bug is a read of `master->flags` at fixed offset 0xb0 from a NULL pointer, which faults immediately; no memory contents are returned to the attacker and no kernel addresses are disclosed.
- I:NIntegrity impact, none
- There is no write primitive — the defect is a read-side dereference that faults before `master->netdev_ops->ndo_xdp_get_xmit_slave()` is reached, so no kernel data or control flow is modified.
- A:HAvailability impact, high
- The dereference happens in softirq/interrupt context, producing "Kernel panic - not syncing: Fatal exception in interrupt" — a complete system crash rather than a recoverable oops, and it can be re-triggered on every reboot as long as traffic and bond reconfiguration continue.