CVE-2025-21916 usb: atm: cxacru: fix a flaw in existing endpoint checks
A flaw in the cxacru USB ATM driver allows a malicious device to trigger a kernel warning and potential denial of service via improper endpoint validation.
- 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-2025-21916?
CVE-2025-21916 is a medium-severity denial of service vulnerability in Linux kernel, published on 1 Apr 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:
usb: atm: cxacru: fix a flaw in existing endpoint checks
Syzbot once again identified a flaw in usb endpoint checking, see [1]. This time the issue stems from a commit authored by me (2eabb655a968 ("usb: atm: cxacru: fix endpoint checking in cxacru_bind()")).
While using usb_find_common_endpoints() may usually be enough to discard devices with wrong endpoints, in this case one needs more than just finding and identifying the sufficient number of endpoints of correct types - one needs to check the endpoint's address as well.
Since cxacru_bind() fills URBs with CXACRU_EP_CMD address in mind, switch the endpoint verification approach to usb_check_XXX_endpoints() instead to fix incomplete ep testing.
[1] Syzbot report: usb 5-1: BOGUS urb xfer, pipe 3 != type 1 WARNING: CPU: 0 PID: 1378 at drivers/usb/core/urb.c:504 usb_submit_urb+0xc4e/0x18c0 drivers/usb/core/urb.c:503 ... RIP: 0010:usb_submit_urb+0xc4e/0x18c0 drivers/usb/core/urb.c:503 ... Call Trace: <TASK> cxacru_cm+0x3c8/0xe50 drivers/usb/atm/cxacru.c:649 cxacru_card_status drivers/usb/atm/cxacru.c:760 [inline] cxacru_bind+0xcf9/0x1150 drivers/usb/atm/cxacru.c:1223 usbatm_usb_probe+0x314/0x1d30 drivers/usb/atm/usbatm.c:1058 cxacru_usb_probe+0x184/0x220 drivers/usb/atm/cxacru.c:1377 usb_probe_interface+0x641/0xbb0 drivers/usb/core/driver.c:396 really_probe+0x2b9/0xad0 drivers/base/dd.c:658 __driver_probe_device+0x1a2/0x390 drivers/base/dd.c:800 driver_probe_device+0x50/0x430 drivers/base/dd.c:830 ...
Which versions are affected by CVE-2025-21916?
It affects 1 product.
Products include Linux kernel.
How do I fix CVE-2025-21916?
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-2025-21916 being exploited?
There is no known exploitation of CVE-2025-21916 in the wild and no public exploit code.
Other vulnerabilities in Linux kernel
Sources
Also known as BELL-CVE-2025-21916, DEBIAN-CVE-2025-21916, GHSA-q6h7-hvhw-m2p9, ROOT-OS-UBUNTU-2404-CVE-2025-21916, UBUNTU-CVE-2025-21916.