# CVE-2026-64545: net, bpf: check master for NULL in xdp_master_redirect()

Status: published. Published: 2026-07-27. Updated: 2026-11-10.

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.

## Remediation

No remediation reported in collected sources

## Affected products and versions

- Linux / Linux: ≥ 879af96ffd72706c6e3278ea6b45b0b0e37ec5d7; < c99ca049e910d61ddbd28cc2c47242f2bfbb4970 (affected, git); ≥ 879af96ffd72706c6e3278ea6b45b0b0e37ec5d7; < e2a56441233131fe18a76001de347ecda217e40c (affected, git); ≥ 879af96ffd72706c6e3278ea6b45b0b0e37ec5d7; < 3876318ea54e83eb70982b8280a3c5e4e32269bf (affected, git); ≥ 879af96ffd72706c6e3278ea6b45b0b0e37ec5d7; < 4edbcacca09f92b85d3951b6add11894b20a84bc (affected, git); ≥ 879af96ffd72706c6e3278ea6b45b0b0e37ec5d7; < 03b743586a2469744e96e9c1015096d07240935d (affected, git); ≥ 879af96ffd72706c6e3278ea6b45b0b0e37ec5d7; < 89c103d702b25ceb2d097faf854deb47b53b17ff (affected, git); ≥ 879af96ffd72706c6e3278ea6b45b0b0e37ec5d7; < e82d8cc4321c373dc46e741cd2dfdaa7921fddb7 (affected, git). Source: CNA: Linux
- Linux / Linux: 5.15 (affected); ≥ 0; < 5.15 (unaffected, semver); ≥ 5.15.212; ≤ 5.15.* (unaffected, semver); ≥ 6.1.178; ≤ 6.1.* (unaffected, semver); ≥ 6.6.145; ≤ 6.6.* (unaffected, semver); ≥ 6.12.97; ≤ 6.12.* (unaffected, semver); ≥ 6.18.40; ≤ 6.18.* (unaffected, semver); ≥ 7.1.5; ≤ 7.1.* (unaffected, semver); ≥ 7.2; ≤ * (unaffected, original_commit_for_fix). Source: CNA: Linux
- Siemens / SIMATIC S7-1500 CPU 1518-4 PN/DP MFP (6ES7518-4AX00-1AB0): ≥ V3.1.6; < * (affected, custom). Source: ADP: siemens-SADP
- Siemens / SIMATIC S7-1500 CPU 1518-4 PN/DP MFP (6ES7518-4AX00-1AB0): ≥ V3.1.7; < * (affected, custom). Source: ADP: siemens-SADP
- Siemens / SIMATIC S7-1500 CPU 1518-4 PN/DP MFP (6ES7518-4AX00-1AC0): ≥ V3.1.6; < * (affected, custom). Source: ADP: siemens-SADP
- Siemens / SIMATIC S7-1500 CPU 1518-4 PN/DP MFP (6ES7518-4AX00-1AC0): ≥ V3.1.7; < * (affected, custom). Source: ADP: siemens-SADP
- Siemens / SIMATIC S7-1500 CPU 1518F-4 PN/DP MFP (6ES7518-4FX00-1AB0): ≥ V3.1.6; < * (affected, custom). Source: ADP: siemens-SADP
- Siemens / SIMATIC S7-1500 CPU 1518F-4 PN/DP MFP (6ES7518-4FX00-1AB0): ≥ V3.1.7; < * (affected, custom). Source: ADP: siemens-SADP
- Siemens / SIMATIC S7-1500 CPU 1518F-4 PN/DP MFP (6ES7518-4FX00-1AC0): ≥ V3.1.6; < * (affected, custom). Source: ADP: siemens-SADP
- Siemens / SIMATIC S7-1500 CPU 1518F-4 PN/DP MFP (6ES7518-4FX00-1AC0): ≥ V3.1.7; < * (affected, custom). Source: ADP: siemens-SADP
- Siemens / SIPLUS S7-1500 CPU 1518-4 PN/DP MFP (6AG1518-4AX00-4AC0): ≥ V3.1.6; < * (affected, custom). Source: ADP: siemens-SADP
- Siemens / SIPLUS S7-1500 CPU 1518-4 PN/DP MFP (6AG1518-4AX00-4AC0): ≥ V3.1.7; < * (affected, custom). Source: ADP: siemens-SADP

## Severity and prioritization

- CVSS 3.1: 7.5 (high); CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H; source: CNA: Linux

- CVSS 3.1: 7.5 (high); CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H; source: NVD: 416baaa9-dc9f-4396-8d5f-8c081fb06d67

- CISA KEV: No listing in collected sources

- EPSS: 0.58% as of 2026-11-09; percentile 47.90%

- SSVC: exploitation none; automatable yes; technical impact partial; source ADP: CISA-ADP

- Weaknesses: CWE-476

## Exploit evidence

No exploit evidence in collected sources. This is not proof of no exploitation.

## References

- https://git.kernel.org/stable/c/c99ca049e910d61ddbd28cc2c47242f2bfbb4970 (CNA: Linux)

- https://git.kernel.org/stable/c/e2a56441233131fe18a76001de347ecda217e40c (CNA: Linux)

- https://git.kernel.org/stable/c/3876318ea54e83eb70982b8280a3c5e4e32269bf (CNA: Linux)

- https://git.kernel.org/stable/c/4edbcacca09f92b85d3951b6add11894b20a84bc (CNA: Linux)

- https://git.kernel.org/stable/c/03b743586a2469744e96e9c1015096d07240935d (CNA: Linux)

- https://git.kernel.org/stable/c/89c103d702b25ceb2d097faf854deb47b53b17ff (CNA: Linux)

- https://git.kernel.org/stable/c/e82d8cc4321c373dc46e741cd2dfdaa7921fddb7 (CNA: Linux)

- https://cert-portal.siemens.com/productcert/html/ssa-019113.html (ADP: siemens-SADP)

- https://cert-portal.siemens.com/productcert/html/ssa-457936.html (ADP: siemens-SADP)

- https://git.kernel.org/stable/c/03b743586a2469744e96e9c1015096d07240935d (416baaa9-dc9f-4396-8d5f-8c081fb06d67)

- https://git.kernel.org/stable/c/3876318ea54e83eb70982b8280a3c5e4e32269bf (416baaa9-dc9f-4396-8d5f-8c081fb06d67)

- https://git.kernel.org/stable/c/4edbcacca09f92b85d3951b6add11894b20a84bc (416baaa9-dc9f-4396-8d5f-8c081fb06d67)

- https://git.kernel.org/stable/c/89c103d702b25ceb2d097faf854deb47b53b17ff (416baaa9-dc9f-4396-8d5f-8c081fb06d67)

- https://git.kernel.org/stable/c/c99ca049e910d61ddbd28cc2c47242f2bfbb4970 (416baaa9-dc9f-4396-8d5f-8c081fb06d67)

- https://git.kernel.org/stable/c/e2a56441233131fe18a76001de347ecda217e40c (416baaa9-dc9f-4396-8d5f-8c081fb06d67)

- https://git.kernel.org/stable/c/e82d8cc4321c373dc46e741cd2dfdaa7921fddb7 (416baaa9-dc9f-4396-8d5f-8c081fb06d67)

- https://cert-portal.siemens.com/productcert/html/ssa-019113.html (0b142b55-0307-4c5a-b3c9-f314f3fb7c5e)

- https://cert-portal.siemens.com/productcert/html/ssa-457936.html (0b142b55-0307-4c5a-b3c9-f314f3fb7c5e)

## Provenance

- CNA: Linux: https://www.cve.org/CVERecord?id=CVE-2026-64545; retrieved 2026-11-10; source updated 2026-11-10

- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-64545; retrieved 2026-11-04; source updated 2026-11-03

- FIRST EPSS: https://api.first.org/data/v1/epss?cve=CVE-2026-64545; retrieved 2026-11-10; source updated Not reported

Revision: 033b8aad5fa82933509fcab81f118683e9c0e471d548c907a88cd971ad6362b0

Canonical: https://y2.dev/cve/CVE-2026-64545

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