CVE-2023-53671 srcu: Delegate work to the boot cpu if using SRCU_SIZE_SMALL
A kernel bug causes a hang during kdump boot on PowerPC when using specific SRCU configurations, leading to denial of service.
- 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-2023-53671?
CVE-2023-53671 is a medium-severity denial of service vulnerability in Linux kernel, published on 7 Oct 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:
srcu: Delegate work to the boot cpu if using SRCU_SIZE_SMALL
Commit 994f706872e6 ("srcu: Make Tree SRCU able to operate without snp_node array") assumes that cpu 0 is always online. However, there really are situations when some other CPU is the boot CPU, for example, when booting a kdump kernel with the maxcpus=1 boot parameter.
On PowerPC, the kdump kernel can hang as follows: ... [ 1.740036] systemd[1]: Hostname set to <xyz.com> [ 243.686240] INFO: task systemd:1 blocked for more than 122 seconds. [ 243.686264] Not tainted 6.1.0-rc1 #1 [ 243.686272] "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message. [ 243.686281] task:systemd state:D stack:0 pid:1 ppid:0 flags:0x00042000 [ 243.686296] Call Trace: [ 243.686301] [c000000016657640] [c000000016657670] 0xc000000016657670 (unreliable) [ 243.686317] [c000000016657830] [c00000001001dec0] __switch_to+0x130/0x220 [ 243.686333] [c000000016657890] [c000000010f607b8] __schedule+0x1f8/0x580 [ 243.686347] [c000000016657940] [c000000010f60bb4] schedule+0x74/0x140 [ 243.686361] [c0000000166579b0] [c000000010f699b8] schedule_timeout+0x168/0x1c0 [ 243.686374] [c000000016657a80] [c000000010f61de8] __wait_for_common+0x148/0x360 [ 243.686387] [c000000016657b20] [c000000010176bb0] __flush_work.isra.0+0x1c0/0x3d0 [ 243.686401] [c000000016657bb0] [c0000000105f2768] fsnotify_wait_marks_destroyed+0x28/0x40 [ 243.686415] [c000000016657bd0] [c0000000105f21b8] fsnotify_destroy_group+0x68/0x160 [ 243.686428] [c000000016657c40] [c0000000105f6500] inotify_release+0x30/0xa0 [ 243.686440] [c000000016657cb0] [c0000000105751a8] __fput+0xc8/0x350 [ 243.686452] [c000000016657d00] [c00000001017d524] task_work_run+0xe4/0x170 [ 243.686464] [c000000016657d50] [c000000010020e94] do_notify_resume+0x134/0x140 [ 243.686478] [c000000016657d80] [c00000001002eb18] interrupt_exit_user_prepare_main+0x198/0x270 [ 243.686493] [c000000016657de0] [c00000001002ec60] syscall_exit_prepare+0x70/0x180 [ 243.686505] [c000000016657e10] [c00000001000bf7c] system_call_vectored_common+0xfc/0x280 [ 243.686520] --- interrupt: 3000 at 0x7fffa47d5ba4 [ 243.686528] NIP: 00007fffa47d5ba4 LR: 0000000000000000 CTR: 0000000000000000 [ 243.686538] REGS: c000000016657e80 TRAP: 3000 Not tainted (6.1.0-rc1) [ 243.686548] MSR: 800000000000d033 <SF,EE,PR,ME,IR,DR,RI,LE> CR: 42044440 XER: 00000000 [ 243.686572] IRQMASK: 0 [ 243.686572] GPR00: 0000000000000006 00007ffffa606710 00007fffa48e7200 0000000000000000 [ 243.686572] GPR04: 0000000000000002 000000000000000a 0000000000000000 0000000000000001 [ 243.686572] GPR08: 000001000c172dd0 0000000000000000 0000000000000000 0000000000000000 [ 243.686572] GPR12: 0000000000000000 00007fffa4ff4bc0 0000000000000000 0000000000000000 [ 243.686572] GPR16: 0000000000000000 0000000000000000 0000000000000000 0000000000000000 [ 243.686572] GPR20: 0000000132dfdc50 000000000000000e 0000000000189375 0000000000000000 [ 243.686572] GPR24: 00007ffffa606ae0 0000000000000005 000001000c185490 000001000c172570 [ 243.686572] GPR28: 000001000c172990 000001000c184850 000001000c172e00 00007fffa4fedd98 [ 243.686683] NIP [00007fffa47d5ba4] 0x7fffa47d5ba4 [ 243.686691] LR [0000000000000000] 0x0 [ 243.686698] --- interrupt: 3000 [ 243.686708] INFO: task kworker/u16:1:24 blocked for more than 122 seconds. [ 243.686717] Not tainted 6.1.0-rc1 #1 [ 243.686724] "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message. [ 243.686733] task:kworker/u16:1 state:D stack:0 pid:24 ppid:2 flags:0x00000800 [ 243.686747] Workqueue: events_unbound fsnotify_mark_destroy_workfn [ 243.686758] Call Trace: [ 243.686762] [c0000000166736e0] [c00000004fd91000] 0xc00000004fd91000 (unreliable) [ 243.686775] [c0000000166738d0] [c00000001001dec0] __switch_to+0x130/0x220 [ 243.686788] [c000000016673930] [c000000010f607b8] __schedule+0x1f8/0x ---truncated---
Which versions are affected by CVE-2023-53671?
It affects 1 product.
Products include Linux kernel.
How do I fix CVE-2023-53671?
Apply the vendor's patch.
Upgrade, then put limits on request size, rate and nesting depth so one client cannot exhaust the service. More about Denial of service.
Is CVE-2023-53671 being exploited?
There is no known exploitation of CVE-2023-53671 in the wild and no public exploit code.
Other vulnerabilities in Linux kernel
Sources
Also known as BELL-CVE-2023-53671, DEBIAN-CVE-2023-53671, GHSA-9qc3-f88f-6rgp, ROOT-OS-DEBIAN-11-CVE-2023-53671, ROOT-OS-UBUNTU-2204-CVE-2023-53671, UBUNTU-CVE-2023-53671.