CVE Vulnerabilities

CVE-2020-25669

Use After Free

Published: May 26, 2021 | Modified: Nov 07, 2023
CVSS 3.x
7.8
HIGH
Source:
NVD
CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
CVSS 2.x
7.2 HIGH
AV:L/AC:L/Au:N/C:C/I:C/A:C
RedHat/V2
RedHat/V3
4.1 MODERATE
CVSS:3.1/AV:P/AC:L/PR:L/UI:N/S:U/C:L/I:L/A:L
Ubuntu
LOW

A vulnerability was found in the Linux Kernel where the function sunkbd_reinit having been scheduled by sunkbd_interrupt before sunkbd being freed. Though the dangling pointer is set to NULL in sunkbd_disconnect, there is still an alias in sunkbd_reinit causing Use After Free.

Weakness

Referencing memory after it has been freed can cause a program to crash, use unexpected values, or execute code.

Affected Software

Name Vendor Start Version End Version
Linux_kernel Linux * 4.4.245 (excluding)
Linux_kernel Linux 4.5 (including) 4.9.245 (excluding)
Linux_kernel Linux 4.10 (including) 4.14.208 (excluding)
Linux_kernel Linux 4.15 (including) 4.19.159 (excluding)
Linux_kernel Linux 4.20 (including) 5.4.79 (excluding)
Linux_kernel Linux 5.5 (including) 5.9.10 (excluding)
Linux Ubuntu bionic *
Linux Ubuntu esm-infra-legacy/trusty *
Linux Ubuntu focal *
Linux Ubuntu groovy *
Linux Ubuntu precise/esm *
Linux Ubuntu trusty *
Linux Ubuntu trusty/esm *
Linux Ubuntu upstream *
Linux Ubuntu xenial *
Linux-allwinner Ubuntu upstream *
Linux-allwinner-5.19 Ubuntu upstream *
Linux-aws Ubuntu bionic *
Linux-aws Ubuntu focal *
Linux-aws Ubuntu groovy *
Linux-aws Ubuntu trusty *
Linux-aws Ubuntu trusty/esm *
Linux-aws Ubuntu upstream *
Linux-aws Ubuntu xenial *
Linux-aws-5.0 Ubuntu bionic *
Linux-aws-5.0 Ubuntu esm-infra/bionic *
Linux-aws-5.0 Ubuntu upstream *
Linux-aws-5.11 Ubuntu upstream *
Linux-aws-5.13 Ubuntu upstream *
Linux-aws-5.15 Ubuntu upstream *
Linux-aws-5.19 Ubuntu upstream *
Linux-aws-5.3 Ubuntu bionic *
Linux-aws-5.3 Ubuntu esm-infra/bionic *
Linux-aws-5.3 Ubuntu upstream *
Linux-aws-5.4 Ubuntu bionic *
Linux-aws-5.4 Ubuntu upstream *
Linux-aws-5.8 Ubuntu upstream *
Linux-aws-6.2 Ubuntu upstream *
Linux-aws-6.5 Ubuntu upstream *
Linux-aws-6.8 Ubuntu upstream *
Linux-aws-fips Ubuntu fips-updates/bionic *
Linux-aws-fips Ubuntu fips-updates/focal *
Linux-aws-fips Ubuntu fips/bionic *
Linux-aws-fips Ubuntu fips/focal *
Linux-aws-fips Ubuntu trusty *
Linux-aws-fips Ubuntu upstream *
Linux-aws-fips Ubuntu xenial *
Linux-aws-hwe Ubuntu upstream *
Linux-aws-hwe Ubuntu xenial *
Linux-azure Ubuntu bionic *
Linux-azure Ubuntu esm-infra/bionic *
Linux-azure Ubuntu focal *
Linux-azure Ubuntu groovy *
Linux-azure Ubuntu trusty *
Linux-azure Ubuntu trusty/esm *
Linux-azure Ubuntu upstream *
Linux-azure Ubuntu xenial *
Linux-azure-4.15 Ubuntu bionic *
Linux-azure-4.15 Ubuntu upstream *
Linux-azure-5.11 Ubuntu upstream *
Linux-azure-5.13 Ubuntu upstream *
Linux-azure-5.15 Ubuntu upstream *
Linux-azure-5.19 Ubuntu upstream *
Linux-azure-5.3 Ubuntu bionic *
Linux-azure-5.3 Ubuntu esm-infra/bionic *
Linux-azure-5.3 Ubuntu upstream *
Linux-azure-5.4 Ubuntu bionic *
Linux-azure-5.4 Ubuntu upstream *
Linux-azure-5.8 Ubuntu upstream *
Linux-azure-6.2 Ubuntu upstream *
Linux-azure-6.5 Ubuntu upstream *
Linux-azure-6.8 Ubuntu upstream *
Linux-azure-edge Ubuntu bionic *
Linux-azure-edge Ubuntu esm-infra/bionic *
Linux-azure-edge Ubuntu upstream *
Linux-azure-fde Ubuntu focal *
Linux-azure-fde Ubuntu upstream *
Linux-azure-fde-5.15 Ubuntu upstream *
Linux-azure-fde-5.19 Ubuntu upstream *
Linux-azure-fde-6.2 Ubuntu upstream *
Linux-azure-fips Ubuntu fips-updates/bionic *
Linux-azure-fips Ubuntu fips-updates/focal *
Linux-azure-fips Ubuntu fips/bionic *
Linux-azure-fips Ubuntu fips/focal *
Linux-azure-fips Ubuntu trusty *
Linux-azure-fips Ubuntu upstream *
Linux-azure-fips Ubuntu xenial *
Linux-bluefield Ubuntu focal *
Linux-bluefield Ubuntu upstream *
Linux-dell300x Ubuntu bionic *
Linux-dell300x Ubuntu upstream *
Linux-fips Ubuntu fips-updates/bionic *
Linux-fips Ubuntu fips-updates/xenial *
Linux-fips Ubuntu fips/bionic *
Linux-fips Ubuntu fips/focal *
Linux-fips Ubuntu fips/xenial *
Linux-fips Ubuntu upstream *
Linux-gcp Ubuntu bionic *
Linux-gcp Ubuntu esm-infra/bionic *
Linux-gcp Ubuntu focal *
Linux-gcp Ubuntu groovy *
Linux-gcp Ubuntu upstream *
Linux-gcp Ubuntu xenial *
Linux-gcp-4.15 Ubuntu bionic *
Linux-gcp-4.15 Ubuntu upstream *
Linux-gcp-5.11 Ubuntu upstream *
Linux-gcp-5.13 Ubuntu upstream *
Linux-gcp-5.15 Ubuntu upstream *
Linux-gcp-5.19 Ubuntu upstream *
Linux-gcp-5.3 Ubuntu bionic *
Linux-gcp-5.3 Ubuntu esm-infra/bionic *
Linux-gcp-5.3 Ubuntu upstream *
Linux-gcp-5.4 Ubuntu bionic *
Linux-gcp-5.4 Ubuntu upstream *
Linux-gcp-5.8 Ubuntu upstream *
Linux-gcp-6.2 Ubuntu upstream *
Linux-gcp-6.5 Ubuntu upstream *
Linux-gcp-6.8 Ubuntu upstream *
Linux-gcp-edge Ubuntu bionic *
Linux-gcp-edge Ubuntu esm-infra/bionic *
Linux-gcp-edge Ubuntu upstream *
Linux-gcp-fips Ubuntu fips-updates/focal *
Linux-gcp-fips Ubuntu fips/bionic *
Linux-gcp-fips Ubuntu fips/focal *
Linux-gcp-fips Ubuntu trusty *
Linux-gcp-fips Ubuntu upstream *
Linux-gcp-fips Ubuntu xenial *
Linux-gke Ubuntu focal *
Linux-gke Ubuntu upstream *
Linux-gke Ubuntu xenial *
Linux-gke-4.15 Ubuntu bionic *
Linux-gke-4.15 Ubuntu upstream *
Linux-gke-5.0 Ubuntu bionic *
Linux-gke-5.0 Ubuntu upstream *
Linux-gke-5.15 Ubuntu upstream *
Linux-gke-5.3 Ubuntu bionic *
Linux-gke-5.3 Ubuntu upstream *
Linux-gke-5.4 Ubuntu bionic *
Linux-gke-5.4 Ubuntu upstream *
Linux-gkeop Ubuntu focal *
Linux-gkeop Ubuntu upstream *
Linux-gkeop-5.15 Ubuntu upstream *
Linux-gkeop-5.4 Ubuntu bionic *
Linux-gkeop-5.4 Ubuntu upstream *
Linux-hwe Ubuntu bionic *
Linux-hwe Ubuntu esm-infra/bionic *
Linux-hwe Ubuntu upstream *
Linux-hwe Ubuntu xenial *
Linux-hwe-5.11 Ubuntu upstream *
Linux-hwe-5.13 Ubuntu upstream *
Linux-hwe-5.15 Ubuntu upstream *
Linux-hwe-5.19 Ubuntu upstream *
Linux-hwe-5.4 Ubuntu bionic *
Linux-hwe-5.4 Ubuntu upstream *
Linux-hwe-5.8 Ubuntu focal *
Linux-hwe-5.8 Ubuntu upstream *
Linux-hwe-6.2 Ubuntu upstream *
Linux-hwe-6.5 Ubuntu upstream *
Linux-hwe-6.8 Ubuntu upstream *
Linux-hwe-edge Ubuntu bionic *
Linux-hwe-edge Ubuntu esm-infra/bionic *
Linux-hwe-edge Ubuntu esm-infra/xenial *
Linux-hwe-edge Ubuntu upstream *
Linux-hwe-edge Ubuntu xenial *
Linux-ibm Ubuntu upstream *
Linux-ibm-5.15 Ubuntu upstream *
Linux-ibm-5.4 Ubuntu upstream *
Linux-intel Ubuntu upstream *
Linux-intel-5.13 Ubuntu upstream *
Linux-intel-iot-realtime Ubuntu upstream *
Linux-intel-iotg Ubuntu upstream *
Linux-intel-iotg-5.15 Ubuntu upstream *
Linux-iot Ubuntu upstream *
Linux-kvm Ubuntu bionic *
Linux-kvm Ubuntu focal *
Linux-kvm Ubuntu groovy *
Linux-kvm Ubuntu upstream *
Linux-kvm Ubuntu xenial *
Linux-laptop Ubuntu upstream *
Linux-lowlatency Ubuntu upstream *
Linux-lowlatency-hwe-5.15 Ubuntu upstream *
Linux-lowlatency-hwe-5.19 Ubuntu upstream *
Linux-lowlatency-hwe-6.2 Ubuntu upstream *
Linux-lowlatency-hwe-6.5 Ubuntu upstream *
Linux-lowlatency-hwe-6.8 Ubuntu upstream *
Linux-lts-trusty Ubuntu precise/esm *
Linux-lts-trusty Ubuntu upstream *
Linux-lts-xenial Ubuntu trusty *
Linux-lts-xenial Ubuntu trusty/esm *
Linux-lts-xenial Ubuntu upstream *
Linux-nvidia Ubuntu upstream *
Linux-nvidia-6.2 Ubuntu upstream *
Linux-nvidia-6.5 Ubuntu upstream *
Linux-nvidia-6.8 Ubuntu upstream *
Linux-nvidia-lowlatency Ubuntu upstream *
Linux-oem Ubuntu bionic *
Linux-oem Ubuntu esm-infra/bionic *
Linux-oem Ubuntu upstream *
Linux-oem Ubuntu xenial *
Linux-oem-5.10 Ubuntu upstream *
Linux-oem-5.13 Ubuntu upstream *
Linux-oem-5.14 Ubuntu upstream *
Linux-oem-5.17 Ubuntu upstream *
Linux-oem-5.6 Ubuntu focal *
Linux-oem-5.6 Ubuntu upstream *
Linux-oem-6.0 Ubuntu upstream *
Linux-oem-6.1 Ubuntu upstream *
Linux-oem-6.11 Ubuntu upstream *
Linux-oem-6.5 Ubuntu upstream *
Linux-oem-6.8 Ubuntu upstream *
Linux-oem-osp1 Ubuntu bionic *
Linux-oem-osp1 Ubuntu upstream *
Linux-oracle Ubuntu bionic *
Linux-oracle Ubuntu focal *
Linux-oracle Ubuntu groovy *
Linux-oracle Ubuntu upstream *
Linux-oracle Ubuntu xenial *
Linux-oracle-5.0 Ubuntu bionic *
Linux-oracle-5.0 Ubuntu esm-infra/bionic *
Linux-oracle-5.0 Ubuntu upstream *
Linux-oracle-5.11 Ubuntu upstream *
Linux-oracle-5.13 Ubuntu upstream *
Linux-oracle-5.15 Ubuntu upstream *
Linux-oracle-5.3 Ubuntu bionic *
Linux-oracle-5.3 Ubuntu esm-infra/bionic *
Linux-oracle-5.3 Ubuntu upstream *
Linux-oracle-5.4 Ubuntu bionic *
Linux-oracle-5.4 Ubuntu upstream *
Linux-oracle-5.8 Ubuntu upstream *
Linux-oracle-6.5 Ubuntu upstream *
Linux-oracle-6.8 Ubuntu upstream *
Linux-raspi Ubuntu focal *
Linux-raspi Ubuntu groovy *
Linux-raspi Ubuntu upstream *
Linux-raspi-5.4 Ubuntu bionic *
Linux-raspi-5.4 Ubuntu upstream *
Linux-raspi-realtime Ubuntu upstream *
Linux-raspi2 Ubuntu bionic *
Linux-raspi2 Ubuntu focal *
Linux-raspi2 Ubuntu upstream *
Linux-raspi2 Ubuntu xenial *
Linux-raspi2-5.3 Ubuntu bionic *
Linux-raspi2-5.3 Ubuntu upstream *
Linux-realtime Ubuntu jammy *
Linux-realtime Ubuntu upstream *
Linux-riscv Ubuntu focal *
Linux-riscv Ubuntu groovy *
Linux-riscv Ubuntu upstream *
Linux-riscv-5.11 Ubuntu upstream *
Linux-riscv-5.15 Ubuntu upstream *
Linux-riscv-5.19 Ubuntu upstream *
Linux-riscv-5.8 Ubuntu focal *
Linux-riscv-5.8 Ubuntu upstream *
Linux-riscv-6.5 Ubuntu upstream *
Linux-riscv-6.8 Ubuntu upstream *
Linux-snapdragon Ubuntu bionic *
Linux-snapdragon Ubuntu upstream *
Linux-snapdragon Ubuntu xenial *
Linux-starfive Ubuntu upstream *
Linux-starfive-5.19 Ubuntu upstream *
Linux-starfive-6.2 Ubuntu upstream *
Linux-starfive-6.5 Ubuntu upstream *
Linux-xilinx-zynqmp Ubuntu upstream *

Extended Description

The use of previously-freed memory can have any number of adverse consequences, ranging from the corruption of valid data to the execution of arbitrary code, depending on the instantiation and timing of the flaw. The simplest way data corruption may occur involves the system’s reuse of the freed memory. Use-after-free errors have two common and sometimes overlapping causes:

In this scenario, the memory in question is allocated to another pointer validly at some point after it has been freed. The original pointer to the freed memory is used again and points to somewhere within the new allocation. As the data is changed, it corrupts the validly used memory; this induces undefined behavior in the process. If the newly allocated data happens to hold a class, in C++ for example, various function pointers may be scattered within the heap data. If one of these function pointers is overwritten with an address to valid shellcode, execution of arbitrary code can be achieved.

Potential Mitigations

References