high
7.8
CWE
125 787 369
Advisory Published
CVE Published
Updated

CVE-2021-3600: Divide by Zero

First published: Wed Jun 23 2021(Updated: )

A flaw was found in the Linux kernel’s eBPF verification code, where the eBPF 32-bit div/mod source register truncation could lead to out-of-bounds reads and writes. By default, accessing the eBPF verifier is only possible to privileged users with CAP_SYS_ADMIN. This flaw allows a local user who can run eBPF instructions to crash the system or possibly escalate their privileges on the system. The highest threat from this vulnerability is to confidentiality, integrity, as well as system availability.

Credit: security@ubuntu.com

Affected SoftwareAffected VersionHow to fix
redhat/kernel-rt<0:4.18.0-348.rt7.130.el8
0:4.18.0-348.rt7.130.el8
redhat/kernel<0:4.18.0-348.el8
0:4.18.0-348.el8
redhat/Kernel<5.11
5.11
Linux Kernel>=4.14.115<4.14.308
Linux Kernel>=4.15<4.19.206
Linux Kernel>=4.20<5.4.98
Linux Kernel>=5.5<5.10.16
Linux Kernel=5.11-rc1
Linux Kernel=5.11-rc2
Linux Kernel=5.11-rc3
Linux Kernel=5.11-rc4
Linux Kernel=5.11-rc5
Linux Kernel=5.11-rc6
Linux Kernel=5.11-rc7
Ubuntu=14.04
Ubuntu=16.04
Ubuntu=18.04
Red Hat Fedora=34
Red Hat Enterprise Linux=8.0
debian/linux
5.10.223-1
5.10.234-1
6.1.129-1
6.1.133-1
6.12.21-1
6.12.22-1

Remedy

The default Red Hat Enterprise Linux kernel prevents unprivileged users from being able to use eBPF by the kernel.unprivileged_bpf_disabled sysctl. This would require a privileged user with CAP_SYS_ADMIN or root to be able to abuse this flaw reducing its attack space. For the Red Hat Enterprise Linux 7 the eBPF for unprivileged users is always disabled. For the Red Hat Enterprise Linux 8 to confirm the current state, inspect the sysctl with the command: # cat /proc/sys/kernel/unprivileged_bpf_disabled The setting of 1 would mean that unprivileged users can not use eBPF, mitigating the flaw. A kernel update will be required to mitigate the flaw for the root or users with CAP_SYS_ADMIN capabilities.

Remedy

https://git.kernel.org/linus/e88b2c6e5a4d9ce30d75391e4d950da74bb2bd90

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Reference Links

Parent vulnerabilities

(Appears in the following advisories)

Frequently Asked Questions

  • What is the severity of CVE-2021-3600?

    CVE-2021-3600 has a medium severity rating due to its potential for local privilege escalation.

  • How do I fix CVE-2021-3600?

    To fix CVE-2021-3600, upgrade to the kernel versions specified in the remediation details or install the provided patches.

  • What software is affected by CVE-2021-3600?

    CVE-2021-3600 affects various versions of the Linux kernel, specifically those prior to the fixed versions stated in the remediation.

  • Is CVE-2021-3600 exploitable remotely?

    No, CVE-2021-3600 is only exploitable locally by users with specific privileges.

  • What types of vulnerabilities are related to CVE-2021-3600?

    CVE-2021-3600 is related to local privilege escalation through out-of-bounds read and write vulnerabilities.

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