CVE-2025-68258 comedi: multiq3: sanitize config options in multiq3_attach()
A local attacker can cause a denial of service in the Linux kernel comedi multiq3 driver by providing excessive configuration options during device attachment.
- 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-2025-68258?
CVE-2025-68258 is a denial of service vulnerability in Linux, published on 16 Dec 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:
comedi: multiq3: sanitize config options in multiq3_attach()
Syzbot identified an issue [1] in multiq3_attach() that induces a task timeout due to open() or COMEDI_DEVCONFIG ioctl operations, specifically, in the case of multiq3 driver.
This problem arose when syzkaller managed to craft weird configuration options used to specify the number of channels in encoder subdevice. If a particularly great number is passed to s->n_chan in multiq3_attach() via it->options[2], then multiple calls to multiq3_encoder_reset() at the end of driver-specific attach() method will be running for minutes, thus blocking tasks and affected devices as well.
While this issue is most likely not too dangerous for real-life devices, it still makes sense to sanitize configuration inputs. Enable a sensible limit on the number of encoder chips (4 chips max, each with 2 channels) to stop this behaviour from manifesting.
[1] Syzbot crash: INFO: task syz.2.19:6067 blocked for more than 143 seconds. ... Call Trace: <TASK> context_switch kernel/sched/core.c:5254 [inline] __schedule+0x17c4/0x4d60 kernel/sched/core.c:6862 __schedule_loop kernel/sched/core.c:6944 [inline] schedule+0x165/0x360 kernel/sched/core.c:6959 schedule_preempt_disabled+0x13/0x30 kernel/sched/core.c:7016 __mutex_lock_common kernel/locking/mutex.c:676 [inline] __mutex_lock+0x7e6/0x1350 kernel/locking/mutex.c:760 comedi_open+0xc0/0x590 drivers/comedi/comedi_fops.c:2868 chrdev_open+0x4cc/0x5e0 fs/char_dev.c:414 do_dentry_open+0x953/0x13f0 fs/open.c:965 vfs_open+0x3b/0x340 fs/open.c:1097 ...
Which versions are affected by CVE-2025-68258?
How do I fix CVE-2025-68258?
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-2025-68258 being exploited?
There is no known exploitation of CVE-2025-68258 in the wild and no public exploit code.
Sources
Also known as BELL-CVE-2025-68258, DEBIAN-CVE-2025-68258, GHSA-p2q7-w28w-9654, ROOT-OS-DEBIAN-11-CVE-2025-68258, ROOT-OS-DEBIAN-12-CVE-2025-68258, ROOT-OS-DEBIAN-13-CVE-2025-68258 and 3 more.