Incorrect default permissions in Linux kernel - CVE-2019-20908
Published: July 16, 2020 / Updated: August 8, 2020
Vulnerability identifier: #VU34141
CSH Severity: Low
CVSS v4: 8.4 [CVSS:4.0/AV:L/AC:L/AT:N/PR:H/UI:N/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N]
CVE-ID: CVE-2019-20908
CWE-ID: CWE-276
Exploitation vector: Local access
Exploit availability:
No public exploit available
Vulnerability details
The vulnerability allows a local privileged user to execute arbitrary code.
An issue was discovered in drivers/firmware/efi/efi.c in the Linux kernel before 5.4. Incorrect access permissions for the efivar_ssdt ACPI variable could be used by attackers to bypass lockdown or secure boot restrictions, aka CID-1957a85b0032.
Affected software
Linux kernel
Red Hat Enterprise Linux for x86_64
Red Hat Enterprise Linux for IBM z Systems
Red Hat Enterprise Linux for Power, little endian
Red Hat Enterprise Linux for ARM 64
Red Hat CodeReady Linux Builder for x86_64
Red Hat CodeReady Linux Builder for Power, little endian
Red Hat CodeReady Linux Builder for ARM 64
Red Hat Enterprise Linux for Real Time
Red Hat Enterprise Linux for Real Time for NFV
Red Hat CodeReady Linux Builder for ARM 64 - Extended Update Support
Red Hat CodeReady Linux Builder for Power, little endian - Extended Update Support
Red Hat CodeReady Linux Builder for x86_64 - Extended Update Support
Red Hat Enterprise Linux for ARM 64 - Extended Update Support
Red Hat Enterprise Linux for Power, little endian - Extended Update Support
Red Hat Enterprise Linux for IBM z Systems - Extended Update Support
Red Hat Enterprise Linux for x86_64 - Extended Update Support
Red Hat Enterprise Linux Server - TUS
Red Hat Enterprise Linux Server - AUS
kernel (Red Hat package)
kernel-rt (Red Hat package)
Red Hat Enterprise Linux for x86_64
Red Hat Enterprise Linux for IBM z Systems
Red Hat Enterprise Linux for Power, little endian
Red Hat Enterprise Linux for ARM 64
Red Hat CodeReady Linux Builder for x86_64
Red Hat CodeReady Linux Builder for Power, little endian
Red Hat CodeReady Linux Builder for ARM 64
Red Hat Enterprise Linux for Real Time
Red Hat Enterprise Linux for Real Time for NFV
Red Hat CodeReady Linux Builder for ARM 64 - Extended Update Support
Red Hat CodeReady Linux Builder for Power, little endian - Extended Update Support
Red Hat CodeReady Linux Builder for x86_64 - Extended Update Support
Red Hat Enterprise Linux for ARM 64 - Extended Update Support
Red Hat Enterprise Linux for Power, little endian - Extended Update Support
Red Hat Enterprise Linux for IBM z Systems - Extended Update Support
Red Hat Enterprise Linux for x86_64 - Extended Update Support
Red Hat Enterprise Linux Server - TUS
Red Hat Enterprise Linux Server - AUS
kernel (Red Hat package)
kernel-rt (Red Hat package)
How to mitigate CVE-2019-20908
Install update from vendor's website.
Linux kernel - update to 5.4
kernel (Red Hat package) - addressed in versions 4.18.0-80.27.2.el8_0, 4.18.0-147.24.2.el8_1, 4.18.0-193.14.3.el8_2
kernel-rt (Red Hat package) - update to 4.18.0-193.14.3.rt13.67.el8_2
kernel (Red Hat package) - addressed in versions 4.18.0-80.27.2.el8_0, 4.18.0-147.24.2.el8_1, 4.18.0-193.14.3.el8_2
kernel-rt (Red Hat package) - update to 4.18.0-193.14.3.rt13.67.el8_2
External References
- http://lists.opensuse.org/opensuse-security-announce/2020-08/msg00009.html
- http://www.openwall.com/lists/oss-security/2020/07/20/6
- http://www.openwall.com/lists/oss-security/2020/07/29/3
- http://www.openwall.com/lists/oss-security/2020/07/30/2
- http://www.openwall.com/lists/oss-security/2020/07/30/3
- https://cdn.kernel.org/pub/linux/kernel/v5.x/ChangeLog-5.4
- https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=1957a85b0032a81e6482ca4aab883643b8dae06e
- https://git.zx2c4.com/american-unsigned-language/tree/american-unsigned-language.sh
- https://mailarchives.bentasker.co.uk/Mirrors/OSSSec/2020/06-Jun/msg00035.html
- https://usn.ubuntu.com/4426-1/
- https://usn.ubuntu.com/4427-1/
- https://usn.ubuntu.com/4439-1/
- https://usn.ubuntu.com/4440-1/