CVE-2023-53072 mptcp: use the workqueue to destroy unaccepted sockets

High 7.8 Published 2 May 2025 Updated 15 Oct 2026

A use-after-free vulnerability in the Linux kernel's MPTCP subsystem allows local attackers to potentially execute code or escalate privileges.

Exploited in the wild: Not known
Login needed: Any signed-in user
Attackable: Local or same network only
Victim action needed: Not needed
Fix: Available

What is CVE-2023-53072?

CVE-2023-53072 is a high-severity use after free vulnerability in Linux kernel, published on 2 May 2025. It can only be exploited from the same machine or local network, with no action from the victim.

Official description

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

mptcp: use the workqueue to destroy unaccepted sockets

Christoph reported a UaF at token lookup time after having refactored the passive socket initialization part:

BUG: KASAN: use-after-free in __token_bucket_busy+0x253/0x260 Read of size 4 at addr ffff88810698d5b0 by task syz-executor653/3198

CPU: 1 PID: 3198 Comm: syz-executor653 Not tainted 6.2.0-rc59af4eaa31c1f6c00c8f1e448ed99a45c66340dd5 #6 Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS rel-1.13.0-0-gf21b5a4aeb02-prebuilt.qemu.org 04/01/2014 Call Trace: <TASK> dump_stack_lvl+0x6e/0x91 print_report+0x16a/0x46f kasan_report+0xad/0x130 __token_bucket_busy+0x253/0x260 mptcp_token_new_connect+0x13d/0x490 mptcp_connect+0x4ed/0x860 __inet_stream_connect+0x80e/0xd90 tcp_sendmsg_fastopen+0x3ce/0x710 mptcp_sendmsg+0xff1/0x1a20 inet_sendmsg+0x11d/0x140 __sys_sendto+0x405/0x490 __x64_sys_sendto+0xdc/0x1b0 do_syscall_64+0x3b/0x90 entry_SYSCALL_64_after_hwframe+0x72/0xdc

We need to properly clean-up all the paired MPTCP-level resources and be sure to release the msk last, even when the unaccepted subflow is destroyed by the TCP internals via inet_child_forget().

We can re-use the existing MPTCP_WORK_CLOSE_SUBFLOW infra, explicitly checking that for the critical scenario: the closed subflow is the MPC one, the msk is not accepted and eventually going through full cleanup.

With such change, __mptcp_destroy_sock() is always called on msk sockets, even on accepted ones. We don't need anymore to transiently drop one sk reference at msk clone time.

Please note this commit depends on the parent one:

mptcp: refactor passive socket initialization

Weakness: CWE-416

Which versions are affected by CVE-2023-53072?

It affects 1 product.

Products include Linux kernel.

How do I fix CVE-2023-53072?

Apply the vendor's patch.

Upgrade to the fixed version. These bugs are found with fuzzing and sanitisers and avoided by memory-safe languages. More about Use after free.

Is CVE-2023-53072 being exploited?

There is no known exploitation of CVE-2023-53072 in the wild and no public exploit code.

All Linux kernel vulnerabilities

Sources

Also known as BELL-CVE-2023-53072, DEBIAN-CVE-2023-53072, GHSA-r22j-fw7c-mp4g, ROOT-OS-DEBIAN-11-CVE-2023-53072, ROOT-OS-UBUNTU-2204-CVE-2023-53072, UBUNTU-CVE-2023-53072.