In the Linux kernel, the following vulnerability has been resolved:
net: fix fanout UAF in packet_release() via NETDEV_UP race
`packet_release()` has a race window where `NETDEV_UP` can re-register a
socket into a fanout group's `arr[]` array. The re-registration is not
cleaned up by `fanout_release()`, leaving a dangling pointer in the fanout
array.
`packet_release()` does NOT zero `po->num` in its `bind_lock` section.
After releasing `bind_lock`, `po->num` is still non-zero and `po->ifindex`
still matches the bound device. A concurrent `packet_notifier(NETDEV_UP)`
that already found the socket in `sklist` can re-register the hook.
For fanout sockets, this re-registration calls `__fanout_link(sk, po)`
which adds the socket back into `f->arr[]` and increments `f->num_members`,
but does NOT increment `f->sk_ref`.
The fix sets `po->num` to zero in `packet_release` while `bind_lock` is
held to prevent NETDEV_UP from linking, preventing the race window.
This bug was found following an additional audit with Claude Code based
on CVE-2025-38617.
References
Configurations
Configuration 1 (hide)
|
History
11 Nov 2026, 23:10
| Type | Values Removed | Values Added |
|---|---|---|
| Summary |
|
19 Oct 2026, 19:17
| Type | Values Removed | Values Added |
|---|---|---|
| CWE | CWE-362 |
15 Oct 2026, 02:19
| Type | Values Removed | Values Added |
|---|---|---|
| References |
|
Information
Published : 2026-04-22 14:16
Updated : 2026-11-11 23:10
NVD link : CVE-2026-31504
Mitre link : CVE-2026-31504
CVE.ORG link : CVE-2026-31504
JSON object : View
Products Affected
linux
- linux_kernel
