#VU94154 Input validation error in Linux kernel - CVE-2020-27673

Vulnerability identifier: #VU94154

Vulnerability risk: Low

CVSSv4.0: 4.3 [CVSS:4.0/AV:L/AC:L/AT:N/PR:L/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N/E:U/U:Clear]

CVE-ID: CVE-2020-27673

CWE-ID: CWE-20

Exploitation vector: Local

Exploit availability: No

Vulnerable software:
Linux kernel
Operating systems & Components / Operating system

Vendor: Linux Foundation

Description

The vulnerability allows a local user to perform a denial of service (DoS) attack.

The vulnerability exists due to improper input validation within the clear_linked(), consume_one_event(), __evtchn_fifo_handle_events() and evtchn_fifo_percpu_init() functions in drivers/xen/events/events_fifo.c, within the module_param(), DEFINE_RWLOCK(), enable_dynirq(), notify_remote_via_irq(), EXPORT_SYMBOL_GPL(), xen_irq_init(), xen_free_irq(), xen_send_IPI_one(), __xen_evtchn_do_upcall(), xen_setup_callback_vector(), xen_evtchn_cpu_prepare() and xen_init_IRQ() functions in drivers/xen/events/events_base.c, within the active_evtchns() and evtchn_2l_handle_events() functions in drivers/xen/events/events_2l.c. A local user can perform a denial of service (DoS) attack.

Mitigation
Install update from vendor's website.

Vulnerable software versions

Linux kernel: All versions

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External links
https://xenbits.xen.org/xsa/advisory-332.html
https://github.com/torvalds/linux/commit/e99502f76271d6bc4e374fe368c50c67a1fd3070
https://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git/commit/?id=e99502f76271d6bc4e374fe368c50c67a1fd3070
https://lists.opensuse.org/opensuse-security-announce/2020-10/msg00075.html
https://lists.opensuse.org/opensuse-security-announce/2020-11/msg00025.html
https://security.gentoo.org/glsa/202011-06
https://lists.debian.org/debian-lts-announce/2020/12/msg00015.html
https://lists.debian.org/debian-lts-announce/2020/12/msg00027.html
https://www.openwall.com/lists/oss-security/2021/01/19/6

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Q & A

Can this vulnerability be exploited remotely?

No. This vulnerability can be exploited locally. The attacker should have authentication credentials and successfully authenticate on the system.

Is there known malware, which exploits this vulnerability?

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