CVE-2026-74589

bpf, sockmap: Fix sk_redir use-after-free in send verdict

State: Published
Severity: 8.4 High
Published: Aug 22, 2026
Updated: Oct 16, 2026
Reserved: Aug 15, 2026

Description

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

bpf, sockmap: Fix sk_redir use-after-free in send verdict

sk_psock_msg_verdict() takes a socket reference for psock->sk_redir. tcp_bpf_send_verdict() copies that pointer while holding the source socket lock, but does not take a reference for the local copy before dropping the lock around tcp_bpf_sendmsg_redir().

When apply_bytes keeps the cached verdict active, another sendmsg() on the same source socket can consume the remaining bytes and release the cached reference while the first thread still holds only the raw local pointer:

CPU 0 CPU 1 sk_redir = psock->sk_redir apply_bytes remains nonzero release_sock(sk) lock_sock(sk) apply_bytes reaches zero psock->sk_redir = NULL release_sock(sk) tcp_bpf_sendmsg_redir(sk_redir) sock_put(sk_redir) tcp_bpf_sendmsg_redir(sk_redir)

The final sock_put() can free sk_redir before CPU 0 dereferences it.

KASAN reported:

BUG: KASAN: slab-use-after-free in tcp_bpf_sendmsg_redir+0xf39/0x1020 Read of size 8 at addr ffff888108537090 by task poc/87 Call Trace: tcp_bpf_sendmsg_redir+0xf39/0x1020 tcp_bpf_sendmsg+0x977/0x1a50 __sys_sendto+0x32c/0x3a0 __x64_sys_sendto+0xdb/0x1b0 Allocated by task 85: sk_prot_alloc+0x56/0x210 sk_clone+0x6f/0x14b0 inet_csk_clone_lock+0x24/0x740 tcp_create_openreq_child+0x25/0x2710 tcp_v4_syn_recv_sock+0x10a/0xe00 Freed by task 0: __kasan_slab_free+0x43/0x70 slab_free_after_rcu_debug+0xa6/0x1e0 rcu_core+0x50a/0x1850 Last potentially related work creation: __sk_destruct+0x3da/0x540 sk_psock_destroy+0x81e/0xab0 process_one_work+0x63a/0x1070

Take a temporary socket reference while the source socket lock still protects psock->sk_redir, and drop it after tcp_bpf_sendmsg_redir() returns. This keeps each unlocked use independent of cached-verdict ownership.

Scores

CVSS	Score	Vector	Source
3.1	8.4 High	CVSS:3.1/AV:L/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H	Linux

Weaknesses

The record names no weakness.

Affected Products

Product	Versions
LinuxLinux	604326b41a6fb9b4a78b6179335decee0365cd8c to before 41b7da0cb72ca5aa1e62b68dab323d0791fc6bdfAffected 604326b41a6fb9b4a78b6179335decee0365cd8c to before 9b4fbc371a6ecf1b4e43b5a629015cc0830d8de3Affected 604326b41a6fb9b4a78b6179335decee0365cd8c to before 90a19b0894ba79a699b48cf44421b36fbd566e99Affected 604326b41a6fb9b4a78b6179335decee0365cd8c to before d192cff2a37d59206dabe6ec2e60ceac6271f274Affected 604326b41a6fb9b4a78b6179335decee0365cd8c to before 4c9d9aa809c261dc0490a0e19d675f7e8e4c85bfAffected 604326b41a6fb9b4a78b6179335decee0365cd8c to before a14e4ef1d90c3418f01b3b6b8fd3a40a0a208a10Affected 604326b41a6fb9b4a78b6179335decee0365cd8c to before 1cec526cf0a2227395f2c2f4b671cb052ff0b00eAffected 604326b41a6fb9b4a78b6179335decee0365cd8c to before a76624733730e541e4955fdecf506af2f6b20558Affected
LinuxLinux	4.20Affected before 4.20Not affected 5.10.265 through 5.10.Not affected 5.15.216 through 5.15.Not affected 6.1.183 through 6.1.Not affected 6.6.152 through 6.6.Not affected 6.12.104 through 6.12.Not affected 6.18.45 through 6.18.Not affected 7.1.9 through 7.1.*Not affected 7.2 and laterNot affected

Product

Versions

LinuxLinux

604326b41a6fb9b4a78b6179335decee0365cd8c to before 41b7da0cb72ca5aa1e62b68dab323d0791fc6bdfAffected
604326b41a6fb9b4a78b6179335decee0365cd8c to before 9b4fbc371a6ecf1b4e43b5a629015cc0830d8de3Affected
604326b41a6fb9b4a78b6179335decee0365cd8c to before 90a19b0894ba79a699b48cf44421b36fbd566e99Affected
604326b41a6fb9b4a78b6179335decee0365cd8c to before d192cff2a37d59206dabe6ec2e60ceac6271f274Affected
604326b41a6fb9b4a78b6179335decee0365cd8c to before 4c9d9aa809c261dc0490a0e19d675f7e8e4c85bfAffected
604326b41a6fb9b4a78b6179335decee0365cd8c to before a14e4ef1d90c3418f01b3b6b8fd3a40a0a208a10Affected
604326b41a6fb9b4a78b6179335decee0365cd8c to before 1cec526cf0a2227395f2c2f4b671cb052ff0b00eAffected
604326b41a6fb9b4a78b6179335decee0365cd8c to before a76624733730e541e4955fdecf506af2f6b20558Affected

LinuxLinux

4.20Affected
before 4.20Not affected
5.10.265 through 5.10.*Not affected
5.15.216 through 5.15.*Not affected
6.1.183 through 6.1.*Not affected
6.6.152 through 6.6.*Not affected
6.12.104 through 6.12.*Not affected
6.18.45 through 6.18.*Not affected
7.1.9 through 7.1.*Not affected
7.2 and laterNot affected

References

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