high
7.8
CWE
787
Advisory Published
Updated

CVE-2023-31436

First published: Fri Apr 28 2023(Updated: )

A flaw in the Linux Kernel found. A heap out-of-bounds read vulnerability in the Linux Kernel traffic control (QoS) subsystem can be exploited to achieve local privilege escalation. The qfq_change_class function does not properly limit the lmax variable which can lead to out-of-bounds read/write. If the TCA_QFQ_LMAX value is not offered through nlattr, lmax is determined by the MTU value of the network device. The MTU of the loopback device can be set up to 2^31-1 and as a result, it is possible to have an lmax value that exceeds QFQ_MIN_LMAX. Reference: <a href="https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=3037933448f60f9acb705997eae62013ecb81e0d">https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=3037933448f60f9acb705997eae62013ecb81e0d</a>

Credit: cve@mitre.org cve@mitre.org cve@mitre.org

Affected SoftwareAffected VersionHow to fix
Linux Kernel>=3.7<4.14.314
Linux Kernel>=4.15<4.19.282
Linux Kernel>=4.20<5.4.242
Linux Kernel>=5.5.0<5.10.179
Linux Kernel>=5.11<5.15.109
Linux Kernel>=5.16<6.1.26
Linux Kernel>=6.2<6.2.13
debian/linux
5.10.223-1
5.10.226-1
6.1.123-1
6.1.128-1
6.12.12-1
6.12.13-1
IBM Security Verify Governance - Identity Manager<=ISVG 10.0.2
IBM Security Verify Governance, Identity Manager<=ISVG 10.0.2

Remedy

https://cdn.kernel.org/pub/linux/kernel/v6.x/ChangeLog-6.2.13

Remedy

https://github.com/torvalds/linux/commit/3037933448f60f9acb705997eae62013ecb81e0d

Remedy

https://www.spinics.net/lists/stable-commits/msg294885.html

Remedy

If not needed, disable the ability for unprivileged users to create namespaces. To do this temporarily, do: sudo sysctl -w kernel.unprivileged_userns_clone=0 To disable across reboots, do: echo kernel.unprivileged_userns_clone=0 | \ sudo tee /etc/sysctl.d/99-disable-unpriv-userns.conf

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Reference Links

Parent vulnerabilities

(Appears in the following advisories)

Frequently Asked Questions

  • What is the severity of CVE-2023-31436?

    CVE-2023-31436 is classified as a high-severity vulnerability due to its potential for local privilege escalation.

  • How do I fix CVE-2023-31436?

    To mitigate CVE-2023-31436, update the Linux Kernel to a version that has addressed this vulnerability, such as 5.10.223-1 or a later release.

  • Which systems are affected by CVE-2023-31436?

    CVE-2023-31436 affects various versions of the Linux Kernel ranging from 3.7 up to 6.2.13, as well as IBM Security Verify Governance components up to version ISVG 10.0.2.

  • What kind of exploit is possible with CVE-2023-31436?

    CVE-2023-31436 can be exploited to perform a heap out-of-bounds read, potentially leading to unauthorized access to kernel memory.

  • Is there a workaround for CVE-2023-31436 if I cannot upgrade?

    There is no effective workaround for CVE-2023-31436, so upgrading to a patched version is strongly recommended.

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