CVE-2026-53033

In the Linux kernel, the following vulnerability has been resolved:

bpf, sockmap: Take state lock for af_unix iter

When a BPF iterator program updates a sockmap, there is a race condition in unix_stream_bpf_update_proto() where the peer pointer can become stale[1] during a state transition TCP_ESTABLISHED -> TCP_CLOSE.

    CPU0 bpf                          CPU1 close
    --------                          ----------

// unix_stream_bpf_update_proto() sk_pair = unix_peer(sk) if (unlikely(!sk_pair)) return -EINVAL; // unix_release_sock() skpair = unix_peer(sk); unix_peer(sk) = NULL; sock_put(skpair) sock_hold(sk_pair) // UaF

More practically, this fix guarantees that the iterator program is consistently provided with a unix socket that remains stable during iterator execution.

[1]: BUG: KASAN: slab-use-after-free in unix_stream_bpf_update_proto+0x155/0x490 Write of size 4 at addr ffff8881178c9a00 by task test_progs/2231 Call Trace: dump_stack_lvl+0x5d/0x80 print_report+0x170/0x4f3 kasan_report+0xe4/0x1c0 kasan_check_range+0x125/0x200 unix_stream_bpf_update_proto+0x155/0x490 sock_map_link+0x71c/0xec0 sock_map_update_common+0xbc/0x600 sock_map_update_elem+0x19a/0x1f0 bpf_prog_bbbf56096cdd4f01_selective_dump_unix+0x20c/0x217 bpf_iter_run_prog+0x21e/0xae0 bpf_iter_unix_seq_show+0x1e0/0x2a0 bpf_seq_read+0x42c/0x10d0 vfs_read+0x171/0xb20 ksys_read+0xff/0x200 do_syscall_64+0xf7/0x5e0 entry_SYSCALL_64_after_hwframe+0x76/0x7e

Allocated by task 2236: kasan_save_stack+0x30/0x50 kasan_save_track+0x14/0x30 __kasan_slab_alloc+0x63/0x80 kmem_cache_alloc_noprof+0x1d5/0x680 sk_prot_alloc+0x59/0x210 sk_alloc+0x34/0x470 unix_create1+0x86/0x8a0 unix_stream_connect+0x318/0x15b0 __sys_connect+0xfd/0x130 __x64_sys_connect+0x72/0xd0 do_syscall_64+0xf7/0x5e0 entry_SYSCALL_64_after_hwframe+0x76/0x7e

Freed by task 2236: kasan_save_stack+0x30/0x50 kasan_save_track+0x14/0x30 kasan_save_free_info+0x3b/0x70 __kasan_slab_free+0x47/0x70 kmem_cache_free+0x11c/0x590 __sk_destruct+0x432/0x6e0 unix_release_sock+0x9b3/0xf60 unix_release+0x8a/0xf0 __sock_release+0xb0/0x270 sock_close+0x18/0x20 __fput+0x36e/0xac0 fput_close_sync+0xe5/0x1a0 __x64_sys_close+0x7d/0xd0 do_syscall_64+0xf7/0x5e0 entry_SYSCALL_64_after_hwframe+0x76/0x7e

Weakness

The product reuses or references memory after it has been freed. At some point afterward, the memory may be allocated again and saved in another pointer, while the original pointer references a location somewhere within the new allocation. Any operations using the original pointer are no longer valid because the memory “belongs” to the code that operates on the new pointer.

Affected Software

Potential Mitigations

References

• https://git.kernel.org/stable/c/1a59cc6b65fd3ad9915aae5970d859109d4ce9fb
• https://git.kernel.org/stable/c/64c2f93fc3254d3bf5de4445fb732ee5c451edb6
• https://git.kernel.org/stable/c/921920c34cb591947dd30c692500795a69f1e3fa
• https://git.kernel.org/stable/c/98f744d204e5d6fca589cd2c44c3190a0c71697f
• https://git.kernel.org/stable/c/c6f4015eac2e3cbc3cb7a17539e10bbb5c2049c3
• https://git.kernel.org/stable/c/d0d124dbcef9318e326956137b31671407094bd4
• https://access.redhat.com/security/cve/CVE-2026-53033
• https://bugzilla.redhat.com/show_bug.cgi?id=2492281
• https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-53033.json