high
8.8
CWE
787 119
Advisory Published
CVE Published
Updated
Advisory Published

CVE-2021-3489: (Pwn2Own) Canonical Ubuntu eBPF Out-Of-Bounds Access Privilege Escalation Vulnerability

First published: Tue May 11 2021(Updated: )

A flaw out of bound memory write in the Linux kernel BPF subsystem was found in the way user writes to BPF ring buffer too fast, so larger buffer than available memory could be allocated. A local user could use this flaw to crash the system or possibly escalate their privileges on the system.

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<5.13
5.13
Linux kernel>=5.8<5.10.37
Linux kernel>=5.11<5.11.21
Linux kernel>=5.12<5.12.4
Linux kernel=5.13
Linux kernel=5.13-rc1
Linux kernel=5.13-rc2
Linux kernel=5.13-rc3
Ubuntu Linux=20.04
Ubuntu Linux=20.10
Ubuntu Linux=21.04
Ubuntu Unattended Upgrades
debian/linux
5.10.223-1
5.10.234-1
6.1.129-1
6.1.135-1
6.12.22-1
6.12.25-1

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/pub/scm/linux/kernel/git/bpf/bpf.git/commit/?id=4b81ccebaeee885ab1aa1438133f2991e3a2b6ea

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Reference Links

Parent vulnerabilities

(Appears in the following advisories)

Frequently Asked Questions

  • What is the severity of CVE-2021-3489?

    CVE-2021-3489 is considered a high severity vulnerability due to its potential to allow local users to crash the system or escalate privileges.

  • How do I fix CVE-2021-3489?

    To remediate CVE-2021-3489, update the affected Linux kernel to version 4.18.0-348.rt7.130.el8, 4.18.0-348.el8, or 5.13 and above as recommended.

  • What affected systems are impacted by CVE-2021-3489?

    CVE-2021-3489 affects various versions of the Linux kernel, particularly versions between 4.18 and 5.13.

  • Can CVE-2021-3489 be exploited remotely?

    CVE-2021-3489 requires local access for exploitation, making it a local privilege escalation vulnerability rather than a remote one.

  • What are the possible impacts of CVE-2021-3489?

    The impacts of CVE-2021-3489 include system crashes and potential privilege escalation for local users.

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