Linux Kernel up to 6.6.71/6.12.9/6.13-rc6 sysctl null pointer dereference

Summaryinfo

A vulnerability classified as critical has been found in Linux Kernel up to 6.6.71/6.12.9/6.13-rc6. This impacts an unknown function of the component sysctl. This manipulation causes null pointer dereference. This vulnerability appears as CVE-2025-21642. There is no available exploit. It is recommended to upgrade the affected component.

Detailsinfo

A vulnerability was found in Linux Kernel up to 6.6.71/6.12.9/6.13-rc6. It has been declared as critical. Affected by this vulnerability is some unknown processing of the component sysctl. The manipulation with an unknown input leads to a null pointer dereference vulnerability. The CWE definition for the vulnerability is CWE-476. A NULL pointer dereference occurs when the application dereferences a pointer that it expects to be valid, but is NULL, typically causing a crash or exit. As an impact it is known to affect availability. The summary by CVE is:

In the Linux kernel, the following vulnerability has been resolved: mptcp: sysctl: sched: avoid using current->nsproxy Using the 'net' structure via 'current' is not recommended for different reasons. First, if the goal is to use it to read or write per-netns data, this is inconsistent with how the "generic" sysctl entries are doing: directly by only using pointers set to the table entry, e.g. table->data. Linked to that, the per-netns data should always be obtained from the table linked to the netns it had been created for, which may not coincide with the reader's or writer's netns. Another reason is that access to current->nsproxy->netns can oops if attempted when current->nsproxy had been dropped when the current task is exiting. This is what syzbot found, when using acct(2): Oops: general protection fault, probably for non-canonical address 0xdffffc0000000005: 0000 [#1] PREEMPT SMP KASAN PTI KASAN: null-ptr-deref in range [0x0000000000000028-0x000000000000002f] CPU: 1 UID: 0 PID: 5924 Comm: syz-executor Not tainted 6.13.0-rc5-syzkaller-00004-gccb98ccef0e5 #0 Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 09/13/2024 RIP: 0010:proc_scheduler+0xc6/0x3c0 net/mptcp/ctrl.c:125 Code: 03 42 80 3c 38 00 0f 85 fe 02 00 00 4d 8b a4 24 08 09 00 00 48 b8 00 00 00 00 00 fc ff df 49 8d 7c 24 28 48 89 fa 48 c1 ea 03 3c 02 00 0f 85 cc 02 00 00 4d 8b 7c 24 28 48 8d 84 24 c8 00 00 RSP: 0018:ffffc900034774e8 EFLAGS: 00010206 RAX: dffffc0000000000 RBX: 1ffff9200068ee9e RCX: ffffc90003477620 RDX: 0000000000000005 RSI: ffffffff8b08f91e RDI: 0000000000000028 RBP: 0000000000000001 R08: ffffc90003477710 R09: 0000000000000040 R10: 0000000000000040 R11: 00000000726f7475 R12: 0000000000000000 R13: ffffc90003477620 R14: ffffc90003477710 R15: dffffc0000000000 FS: 0000000000000000(0000) GS:ffff8880b8700000(0000) knlGS:0000000000000000 CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 CR2: 00007fee3cd452d8 CR3: 000000007d116000 CR4: 00000000003526f0 DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000 DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400 Call Trace: proc_sys_call_handler+0x403/0x5d0 fs/proc/proc_sysctl.c:601 __kernel_write_iter+0x318/0xa80 fs/read_write.c:612 __kernel_write+0xf6/0x140 fs/read_write.c:632 do_acct_process+0xcb0/0x14a0 kernel/acct.c:539 acct_pin_kill+0x2d/0x100 kernel/acct.c:192 pin_kill+0x194/0x7c0 fs/fs_pin.c:44 mnt_pin_kill+0x61/0x1e0 fs/fs_pin.c:81 cleanup_mnt+0x3ac/0x450 fs/namespace.c:1366 task_work_run+0x14e/0x250 kernel/task_work.c:239 exit_task_work include/linux/task_work.h:43 [inline] do_exit+0xad8/0x2d70 kernel/exit.c:938 do_group_exit+0xd3/0x2a0 kernel/exit.c:1087 get_signal+0x2576/0x2610 kernel/signal.c:3017 arch_do_signal_or_restart+0x90/0x7e0 arch/x86/kernel/signal.c:337 exit_to_user_mode_loop kernel/entry/common.c:111 [inline] exit_to_user_mode_prepare include/linux/entry-common.h:329 [inline] __syscall_exit_to_user_mode_work kernel/entry/common.c:207 [inline] syscall_exit_to_user_mode+0x150/0x2a0 kernel/entry/common.c:218 do_syscall_64+0xda/0x250 arch/x86/entry/common.c:89 entry_SYSCALL_64_after_hwframe+0x77/0x7f RIP: 0033:0x7fee3cb87a6a Code: Unable to access opcode bytes at 0x7fee3cb87a40. RSP: 002b:00007fffcccac688 EFLAGS: 00000202 ORIG_RAX: 0000000000000037 RAX: 0000000000000000 RBX: 00007fffcccac710 RCX: 00007fee3cb87a6a RDX: 0000000000000041 RSI: 0000000000000000 RDI: 0000000000000003 RBP: 0000000000000003 R08: 00007fffcccac6ac R09: 00007fffcccacac7 R10: 00007fffcccac710 R11: 0000000000000202 R12: 00007fee3cd49500 R13: 00007fffcccac6ac R14: 0000000000000000 R15: 00007fee3cd4b000 Modules linked in: ---[ end trace 0000000000000000 ]--- RIP: 0010:proc_scheduler+0xc6/0x3c0 net/mptcp/ctrl.c:125 Code: 03 42 80 3c 38 00 0f 85 fe 02 00 00 4d 8b a4 24 08 09 00 00 48 b8 00 00 00 00 00 fc ---truncated---

It is possible to read the advisory at git.kernel.org. This vulnerability is known as CVE-2025-21642 since 12/29/2024. The exploitation appears to be difficult. The technical details are unknown and an exploit is not publicly available.

The vulnerability scanner Nessus provides a plugin with the ID 230768 (Linux Distros Unpatched Vulnerability : CVE-2025-21642), which helps to determine the existence of the flaw in a target environment.

Upgrading to version 6.6.72, 6.12.10 or 6.13-rc7 eliminates this vulnerability. Applying the patch c0e394fd6b887e84da17e38aaa6c1c104f9c86c2/6035702381c35a8f16757332381e58b348a9eaf9/d38e26e36206ae3d544d496513212ae931d1da0a is able to eliminate this problem. The bugfix is ready for download at git.kernel.org. The best possible mitigation is suggested to be upgrading to the latest version.

The vulnerability is also documented in the databases at Tenable (230768) and CERT Bund (WID-SEC-2025-0119). Be aware that VulDB is the high quality source for vulnerability data.

Affected

• Debian Linux
• Amazon Linux 2
• Red Hat Enterprise Linux
• Ubuntu Linux
• SUSE Linux
• Oracle Linux
• Dell NetWorker
• Dell Avamar
• Dell PowerProtect Data Domain
• Open Source Linux Kernel

Productinfo

Type

• Operating System

Vendor

• Linux

Name

• Kernel

Version

• 6.6.0
• 6.6.1
• 6.6.2
• 6.6.3
• 6.6.4
• 6.6.5
• 6.6.6
• 6.6.7
• 6.6.8
• 6.6.9
• 6.6.10
• 6.6.11
• 6.6.12
• 6.6.13
• 6.6.14
• 6.6.15
• 6.6.16
• 6.6.17
• 6.6.18
• 6.6.19
• 6.6.20
• 6.6.21
• 6.6.22
• 6.6.23
• 6.6.24
• 6.6.25
• 6.6.26
• 6.6.27
• 6.6.28
• 6.6.29
• 6.6.30
• 6.6.31
• 6.6.32
• 6.6.33
• 6.6.34
• 6.6.35
• 6.6.36
• 6.6.37
• 6.6.38
• 6.6.39
• 6.6.40
• 6.6.41
• 6.6.42
• 6.6.43
• 6.6.44
• 6.6.45
• 6.6.46
• 6.6.47
• 6.6.48
• 6.6.49
• 6.6.50
• 6.6.51
• 6.6.52
• 6.6.53
• 6.6.54
• 6.6.55
• 6.6.56
• 6.6.57
• 6.6.58
• 6.6.59
• 6.6.60
• 6.6.61
• 6.6.62
• 6.6.63
• 6.6.64
• 6.6.65
• 6.6.66
• 6.6.67
• 6.6.68
• 6.6.69
• 6.6.70
• 6.6.71
• 6.12.0
• 6.12.1
• 6.12.2
• 6.12.3
• 6.12.4
• 6.12.5
• 6.12.6
• 6.12.7
• 6.12.8
• 6.12.9
• 6.13-rc1
• 6.13-rc2
• 6.13-rc3
• 6.13-rc4
• 6.13-rc5
• 6.13-rc6

License

• open-source

Website

• Vendor: https://www.kernel.org/

CPE 2.3info

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CPE 2.2info

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CVSSv4info

CVSSv3info

CVSSv2info

Exploitinginfo

Threat Intelligenceinfo

Countermeasuresinfo

Timelineinfo

Sourcesinfo

Entryinfo

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