Privilege escalation via USB device in Linux kernel

1) NULL pointer dereference

EUVDB-ID: #VU9515

Risk: Low

CVSSv4.0: 4 [CVSS:4.0/AV:P/AC:L/AT:N/PR:L/UI:N/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N/E:U/U:Clear]

CVE-ID: CVE-2017-15102

CWE-ID: CWE-476 - NULL Pointer Dereference

Exploit availability: No

Description

The vulnerability allows a local user to escalate privileges.

The vulnerability exists due to a race condition and a NULL pointer dereference within tower_probe() function in drivers/usb/misc/legousbtower.c in Linux kernel before  4.8.1. A local user with physical access to the computer and ability to insert USB flash drive can execute arbitrary code with escalated privileges. The USB device would have to delay the control message in tower_probe and accept the control urb in tower_open whilst guest code initiated a write to the device file as tower_delete is called from the error in tower_probe.

According to vendor this security issue exists since 2003.

Mitigation

Install a patch from vendor's repository:
https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=2fae9e5a7babada041e2e1...

Vulnerable software versions

Linux kernel: 4.5 - 4.8

CPE2.3

• cpe:2.3:o:linux_foundation:linux_kernel:4.5.7:*:*:*:*:*:*:*
• cpe:2.3:o:linux_foundation:linux_kernel:4.6.7:*:*:*:*:*:*:*
• cpe:2.3:o:linux_foundation:linux_kernel:4.7.9:*:*:*:*:*:*:*
• cpe:2.3:o:linux_foundation:linux_kernel:4.8:*:*:*:*:*:*:*

External links

https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=2fae9e5a7babada041e2e1...

Q & A

Can this vulnerability be exploited remotely?

No. The attacker should have physical access to the system in order to successfully exploit this vulnerability.

Is there known malware, which exploits this vulnerability?

No. We are not aware of malware exploiting this vulnerability.