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

> A missing NULL check in the Linux kernel's XDP master redirect function allows a local attacker to trigger a kernel panic via a race condition during bond slave release.

- **Severity:** High 7.5 (`CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H`)
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** Yes
- **Published:** 27 Jul 2026
- **Updated:** 19 Oct 2026
- **Also known as:** AZL-94023, BELL-CVE-2026-64545, DEBIAN-CVE-2026-64545, GHSA-5fp4-82x6-8894, ROOT-OS-DEBIAN-12-CVE-2026-64545, UBUNTU-CVE-2026-64545

## What is CVE-2026-64545?

CVE-2026-64545 is a high-severity vulnerability in Linux, published on 27 Jul 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.

### Official 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.

Weakness: CWE-476 (NULL Pointer Dereference)

## Which versions are affected by CVE-2026-64545?


## How do I fix CVE-2026-64545?

Apply the vendor's patch.

## Is CVE-2026-64545 being exploited?

There is no known exploitation of CVE-2026-64545 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-64545 and fix it if it is affected.

What it is: CVE-2026-64545 is a high-severity vulnerability in Linux, published on 27 Jul 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.
Exploitation: There is no known exploitation of CVE-2026-64545 in the wild and no public exploit code.

Affected product: Linux. No package-level version data is available, so check the vendor advisory linked from the reference page.

Task:
1. Search the dependency manifests and lockfiles (for example package.json, package-lock.json, requirements.txt, poetry.lock, uv.lock, pom.xml, build.gradle, go.mod, Cargo.lock, Gemfile.lock) and any Dockerfiles for the affected packages, including transitive dependencies.
2. If an affected version is in use, upgrade it to the fixed version for its release line with the project's package manager, so the lockfile is regenerated. Prefer the smallest upgrade that fixes it.
3. If there is no fix, or the upgrade would break the build, do not guess: explain the risk and the safest workaround instead.
4. Run the tests and summarise what changed and why.
5. If nothing in the project is affected, say so and change nothing.

Reference: https://insights.sbomify.com/CVE-2026-64545/ (Markdown: https://insights.sbomify.com/CVE-2026-64545/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-64545
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-64545
- OSV: https://osv.dev/vulnerability/CVE-2026-64545

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-64545/
Summaries are generated and may contain mistakes; the official description above is the record.