CVE-2025-68194 media: imon: make send_packet() more robust
A flaw in the Linux kernel imon driver causes hung tasks and system stalls due to infinite USB error retries, requiring a local attacker with physical access to trigger.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Local or same network only
- Victim action needed
- Not needed
- Fix
- Available
What is CVE-2025-68194?
CVE-2025-68194 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:
media: imon: make send_packet() more robust
syzbot is reporting that imon has three problems which result in hung tasks due to forever holding device lock [1].
First problem is that when usb_rx_callback_intf0() once got -EPROTO error after ictx->dev_present_intf0 became true, usb_rx_callback_intf0() resubmits urb after printk(), and resubmitted urb causes usb_rx_callback_intf0() to again get -EPROTO error. This results in printk() flooding (RCU stalls).
Alan Stern commented [2] that
In theory it's okay to resubmit _if_ the driver has a robust error-recovery scheme (such as giving up after some fixed limit on the number of errors or after some fixed time has elapsed, perhaps with a time delay to prevent a flood of errors). Most drivers don't bother to do this; they simply give up right away. This makes them more vulnerable to short-term noise interference during USB transfers, but in reality such interference is quite rare. There's nothing really wrong with giving up right away.
but imon has a poor error-recovery scheme which just retries forever; this behavior should be fixed.
Since I'm not sure whether it is safe for imon users to give up upon any error code, this patch takes care of only union of error codes chosen from modules in drivers/media/rc/ directory which handle -EPROTO error (i.e. ir_toy, mceusb and igorplugusb).
Second problem is that when usb_rx_callback_intf0() once got -EPROTO error before ictx->dev_present_intf0 becomes true, usb_rx_callback_intf0() always resubmits urb due to commit 8791d63af0cf ("[media] imon: don't wedge hardware after early callbacks"). Move the ictx->dev_present_intf0 test introduced by commit 6f6b90c9231a ("[media] imon: don't parse scancodes until intf configured") to immediately before imon_incoming_packet(), or the first problem explained above happens without printk() flooding (i.e. hung task).
Third problem is that when usb_rx_callback_intf0() is not called for some reason (e.g. flaky hardware; the reproducer for this problem sometimes prevents usb_rx_callback_intf0() from being called), wait_for_completion_interruptible() in send_packet() never returns (i.e. hung task). As a workaround for such situation, change send_packet() to wait for completion with timeout of 10 seconds.
Which versions are affected by CVE-2025-68194?
How do I fix CVE-2025-68194?
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-2025-68194 being exploited?
There is no known exploitation of CVE-2025-68194 in the wild and no public exploit code.
Sources
Also known as BELL-CVE-2025-68194, DEBIAN-CVE-2025-68194, GHSA-c97r-q83w-hp2r, ROOT-OS-UBUNTU-2204-CVE-2025-68194, ROOT-OS-UBUNTU-2404-CVE-2025-68194, UBUNTU-CVE-2025-68194.