high
7.8
CWE
416
Advisory Published
CVE Published
CVE Published
Updated

CVE-2021-3715: Use After Free

First published: Mon Aug 16 2021(Updated: )

Linux Kernel could allow a local authenticated attacker to gain elevated privileges on the system, caused by a use-after-free in route4_change() in net/sched/cls_route.c. By sending a specially-crafted request, an attacker could exploit this vulnerability to escalate privileges.

Credit: secalert@redhat.com

Affected SoftwareAffected VersionHow to fix
redhat/kernel-rt<0:3.10.0-1160.42.2.rt56.1182.el7
0:3.10.0-1160.42.2.rt56.1182.el7
redhat/kernel<0:3.10.0-1160.42.2.el7
0:3.10.0-1160.42.2.el7
redhat/kernel-rt<0:4.18.0-240.rt7.54.el8
0:4.18.0-240.rt7.54.el8
redhat/kernel<0:4.18.0-240.el8
0:4.18.0-240.el8
redhat/kernel<0:4.18.0-147.54.2.el8_1
0:4.18.0-147.54.2.el8_1
redhat/kernel-rt<0:4.18.0-193.65.2.rt13.117.el8_2
0:4.18.0-193.65.2.rt13.117.el8_2
redhat/kernel<0:4.18.0-193.65.2.el8_2
0:4.18.0-193.65.2.el8_2
redhat/redhat-virtualization-host<0:4.3.18-20210903.0.el7_9
0:4.3.18-20210903.0.el7_9
IBM DRM<=2.0.6
Linux Linux kernel>=3.18<4.4.218
Linux Linux kernel>=4.5<4.9.218
Linux Linux kernel>=4.10<4.14.175
Linux Linux kernel>=4.15<4.19.114
Linux Linux kernel>=4.20<5.4.29
Linux Linux kernel>=5.5.0<5.5.14

Remedy

https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=ef299cc3fa1a9e1288665a9fdc8bff55629fd359

Remedy

In order to mitigate this issue, it is possible to prevent the affected code from being loaded by blacklisting the kernel module cls_route.ko. For instructions relating to how to blacklist a kernel module refer to: https://access.redhat.com/solutions/41278. Alternatively, if cls_route is being used, on Red Hat Enterprise Linux 8, you can disable unprivileged user namespaces by setting user.max_user_namespaces to 0: # echo "user.max_user_namespaces=0" > /etc/sysctl.d/userns.conf # sysctl -p /etc/sysctl.d/userns.conf

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Reference Links

Parent vulnerabilities

(Appears in the following advisories)

Frequently Asked Questions

  • What is CVE-2021-3715?

    CVE-2021-3715 is a vulnerability in the Linux Kernel that could allow a local authenticated attacker to gain elevated privileges on the system.

  • What is the severity of CVE-2021-3715?

    The severity of CVE-2021-3715 is high, with a severity value of 7.8.

  • How does CVE-2021-3715 affect the Linux Kernel?

    CVE-2021-3715 affects the 'Routing decision' classifier in the Linux Kernel's Traffic Control networking subsystem, leading to a use-after-free condition.

  • Who is affected by CVE-2021-3715?

    Unprivileged local users on systems running Linux Kernel versions 3.18 up to 5.10 are affected by CVE-2021-3715.

  • Are there any remedies or patches available for CVE-2021-3715?

    Yes, remedies and patches are available. Please refer to the provided references for more information.

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