CVE-2025-38157: 
Linux Kernel vulnerability analysis and mitigation

CVE-2025-38157 is a divide-by-zero and out-of-bounds read/write vulnerability in the Linux kernel's ath9k_htc WiFi driver. A malicious USB device can send a WMI_SWBA_EVENTID event before beaconing has been enabled, triggering a divide-by-zero error in ath9k_htc_swba() that leads to a kernel crash or out-of-bounds memory access. The vulnerability affects Linux kernel versions from 3.0 through multiple stable branches, with fixed versions including 5.4.295, 5.10.239, 5.15.186, 6.1.142, 6.6.94, 6.12.34, and 6.15.3. It was disclosed on July 3, 2025, and carries a CVSS v3.1 base score of 7.8 (High) (Red Hat CVE, Feedly).

The root cause is insufficient input validation in the ath9k_htc_swba() function of the ath9k_htc USB WiFi driver, classified as CWE-787 (Out-of-bounds Write). When a WMI_SWBA_EVENTID WMI event is received from a USB-attached device before the driver has enabled beaconing, a division operation uses an uninitialized or zero beacon count, resulting in a divide-by-zero error. This can lead to either a kernel panic (crash) or an out-of-bounds memory read, depending on kernel configuration and timing. The fix adds an early-exit guard in ath9k_htc_swba() that aborts processing if beacons are not yet enabled (Red Hat CVE, Kernel Patch).

Successful exploitation can cause a kernel crash (denial of service) or enable out-of-bounds memory reads, potentially exposing sensitive kernel memory contents. Because the attack vector is local (physical USB access required), the scope is limited to the affected host; however, a kernel crash could disrupt all services running on the system. In scenarios where out-of-bounds reads succeed, an attacker may gain unauthorized access to kernel memory, potentially facilitating privilege escalation or information disclosure (Red Hat CVE).

There is no public proof-of-concept exploit and no evidence of in-the-wild exploitation as of the time of disclosure (Feedly). Exploitation requires physical or privileged local access to connect a specially crafted USB WiFi device to the target system. The EPSS score is approximately 0.024% (0.000240), indicating a very low probability of exploitation in the near term. The vulnerability is not listed in the CISA Known Exploited Vulnerabilities catalog.

1. Acquire or craft a malicious USB device: Prepare a USB device (e.g., using a programmable USB microcontroller or a modified ath9k_htc-compatible dongle) capable of sending arbitrary WMI events to the host driver.
2. Gain physical or local access: Connect the malicious USB WiFi device to a target system running a vulnerable Linux kernel (versions 3.0 through the unpatched stable branches).
3. Trigger premature WMI_SWBA_EVENTID: Program the USB device to emit a WMI_SWBA_EVENTID event immediately upon enumeration, before the host driver has completed beacon initialization and enabled beaconing.
4. Induce divide-by-zero: The ath9k_htc_swba() function in the kernel driver processes the event and performs a division using an uninitialized/zero beacon interval value, triggering a divide-by-zero kernel error.
5. Achieve impact: Depending on kernel configuration, the result is either a kernel panic (system crash/denial of service) or an out-of-bounds memory read that may expose kernel memory contents (Red Hat CVE).

• Physical/Hardware: Unexpected or unrecognized USB WiFi device (ath9k_htc-compatible) connected to the system, particularly in environments with strict USB device policies.
• Logs: Kernel logs (dmesg, /var/log/kern.log) showing divide-by-zero errors or oops/panic messages referencing ath9k_htc_swba or the ath9k_htc driver module.
• System Behavior: Sudden kernel panic or system reboot without prior warning; kernel crash dumps (kdump) referencing the ath9k_htc driver.
• Process/Module: Unexpected loading or reloading of the ath9k_htc kernel module coinciding with USB device insertion events.

Update the Linux kernel to a patched version: 5.4.295, 5.10.239, 5.15.186, 6.1.142, 6.6.94, 6.12.34, 6.15.3, or 6.16-rc1 and later. Vendor-specific updates are available for Debian (DSA-5973-1, DLA-4328-1), Ubuntu (USN-7770-1, USN-7774-1/3/4, USN-7775-1/2, USN-7789-2), SUSE, and openSUSE. As a workaround where patching is not immediately possible, restrict or disable USB device connections using USB authorization policies (/sys/bus/usb/devices/*/authorized) or physical port controls to prevent untrusted USB WiFi devices from being connected (Red Hat CVE, Kernel Patch).