UBUNTU-CVE-2026-68399: Use After Free
In the Linux kernel, the following vulnerability has been resolved: bpf: Fix UAF in sock clone early bailouts Similar to recent commit 9b51a6155d14 ("bpf,fork: wipe ->bpfstorage before bailouts that access it"), skclone() performs an initial shallow copy of the socket field ->skbpfstorage via sockcopy() for the cloned socket newsk. If skclone() bails out early (e.g. if skfiltercharge() fails) prior to calling bpfskstorageclone(), newsk->skbpfstorage still points to the parent socket's BPF local storage. When newsk is subsequently freed via skfree(), the deallocation path (skdestruct() -> bpfskstoragefree()) destroys the parent socket's BPF local storage, leading to a use-after-free (UAF) on the parent socket. Fix this by resetting newsk->skbpfstorage to NULL immediately after sockcopy() in skclone(), and remove the now redundant initialization from bpfskstorageclone().
Affected Software
Remediation
Recommended actions to resolve this vulnerability, in priority order.
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Reset newsk->sk_bpf_storage to NULL immediately after sock_copy() in sk_clone(), including before any early bailout such as sk_filter_charge() failure; remove the redundant initialization from bpf_sk_storage_clone().
Linux kernel BPF socket storage handling newsk->sk_bpf_storage = NULL
Event History
Frequently Asked Questions
What conditions are required to trigger the use-after-free?
A socket clone must copy a parent socket that has BPF local storage, and sk_clone() must then exit early before bpf_sk_storage_clone() runs. The description gives failure of sk_filter_charge() as an example of such an early bailout.
What is the impact when the early bailout occurs?
The cloned socket retains a pointer to the parent socket's BPF local storage. When the cloned socket is freed, its cleanup can destroy that parent storage, causing a use-after-free on the parent socket.
Which Ubuntu kernel packages are identified as affected?
The listed packages are linux, linux-azure, linux-gcp, linux-aws-fips, linux-azure-fips, linux-fips, linux-gcp-fips, and linux-realtime.
How does the fix prevent the issue?
The fix clears newsk->sk_bpf_storage immediately after the shallow socket copy in sk_clone(). This prevents an early-failed clone from freeing BPF local storage that belongs to its parent socket.