CVE-2021-31829: Infoleak
First published: Fri Apr 30 2021(Updated: )
A flaw was found in the Linux kernel's eBPF verification code. By default, accessing the eBPF verifier is only accessible to privileged users with CAP_SYS_ADMIN. This flaw allows a local user who can insert eBPF instructions, to use the eBPF verifier to abuse a spectre-like flaw and infer all system memory. The highest threat from this vulnerability is to confidentiality.
Credit: cve@mitre.org
| Affected Software | Affected Version | How 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 |
| debian/linux | 5.10.223-1 5.10.226-1 6.1.123-1 6.1.128-1 6.12.12-1 6.12.16-1 | |
| Linux kernel | <=5.12.1 | |
| Fedora | =32 | |
| Fedora | =33 | |
| Fedora | =34 | |
| Debian | =9.0 |
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 and 8 kernel 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.
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Reference Links
- https://www.cve.org/CVERecord?id=CVE-2021-31829 https://nvd.nist.gov/vuln/detail/CVE-2021-31829
- https://bugzilla.redhat.com/show_bug.cgi?id=1957788
- https://access.redhat.com/errata/RHSA-2021:4140
- https://access.redhat.com/errata/RHSA-2021:4356
- https://access.redhat.com/security/cve/cve-2021-31829
- http://www.openwall.com/lists/oss-security/2021/05/04/4
- https://github.com/torvalds/linux/commit/801c6058d14a82179a7ee17a4b532cac6fad067f
- https://lists.debian.org/debian-lts-announce/2021/06/msg00019.html
- https://lists.fedoraproject.org/archives/list/package-announce@lists.fedoraproject.org/message/VWCZ6LJLENL2C3URW5ICARTACXPFCFN2/
- https://lists.fedoraproject.org/archives/list/package-announce@lists.fedoraproject.org/message/Y4X2G5YAPYJGI3PFEZZNOTRYI33GOCCZ/
- https://lists.fedoraproject.org/archives/list/package-announce@lists.fedoraproject.org/message/ZI7OBCJQDNWMKLBP6MZ5NV4EUTDAMX6Q/
- https://launchpad.net/bugs/cve/CVE-2021-31829
- https://www.openwall.com/lists/oss-security/2021/05/04/4
- https://git.kernel.org/pub/scm/linux/kernel/git/bpf/bpf.git/patch/?id=b9b34ddbe2076ade359cd5ce7537d5ed019e9807
- https://git.kernel.org/pub/scm/linux/kernel/git/bpf/bpf.git/patch/?id=801c6058d14a82179a7ee17a4b532cac6fad067f
- https://bugzilla.redhat.com/show_bug.cgi/show_bug.cgi?id=1957789
- https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/VWCZ6LJLENL2C3URW5ICARTACXPFCFN2/
- https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/Y4X2G5YAPYJGI3PFEZZNOTRYI33GOCCZ/
- https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/ZI7OBCJQDNWMKLBP6MZ5NV4EUTDAMX6Q/
- https://security-tracker.debian.org/tracker/CVE-2021-31829
- https://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2021-31829
- https://nvd.nist.gov/vuln/detail/CVE-2021-31829
- https://ubuntu.com/security/CVE-2021-31829
Frequently Asked Questions
What is the severity of CVE-2021-31829?
CVE-2021-31829 is considered to have a high severity due to its potential impact on system security.
How do I fix CVE-2021-31829?
To fix CVE-2021-31829, update your kernel to versions 0:4.18.0-348.rt7.130.el8, 0:4.18.0-348.el8 for Red Hat, or apply the corresponding updates for your Linux distribution.
Which Linux distributions are affected by CVE-2021-31829?
CVE-2021-31829 affects various Linux distributions including Red Hat, Fedora versions 32, 33, 34, and Debian 9.0.
What kind of vulnerability is CVE-2021-31829?
CVE-2021-31829 is a local privilege escalation vulnerability related to eBPF verification in the Linux kernel.
Who can exploit CVE-2021-31829?
CVE-2021-31829 can be exploited by a local user with the ability to insert eBPF instructions to infer sensitive system information.
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