CVE-2020-27170: Infoleak
First published: Thu Mar 18 2021(Updated: )
A flaw was found in the Linux kernels eBPF verification code. By default accessing the eBPF verifier is only accessible to privileged users with CAP_SYS_ADMIN. A local user with the ability to insert eBPF instructions can use the eBPF verifier to abuse a spectre like flaw where they can infer all system memory.
Credit: cve@mitre.org cve@mitre.org
| Affected Software | Affected Version | How to fix |
|---|---|---|
| redhat/kernel-rt | <0:3.10.0-1160.31.1.rt56.1169.el7 | 0:3.10.0-1160.31.1.rt56.1169.el7 |
| redhat/kernel | <0:3.10.0-1160.31.1.el7 | 0:3.10.0-1160.31.1.el7 |
| Linux Linux kernel | <5.11.8 | |
| Fedoraproject Fedora | =32 | |
| Fedoraproject Fedora | =33 | |
| Fedoraproject Fedora | =34 | |
| Canonical Ubuntu Linux | =14.04 | |
| Canonical Ubuntu Linux | =16.04 | |
| Canonical Ubuntu Linux | =18.04 | |
| Canonical Ubuntu Linux | =20.04 | |
| Debian Debian Linux | =9.0 | |
| IBM DRM | <=2.0.6 | |
| debian/linux | 5.10.223-1 5.10.226-1 6.1.115-1 6.1.112-1 6.11.5-1 6.11.7-1 |
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.
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Reference Links
- https://www.cve.org/CVERecord?id=CVE-2020-27170 https://nvd.nist.gov/vuln/detail/CVE-2020-27170
- https://bugzilla.redhat.com/show_bug.cgi?id=1940627
- https://access.redhat.com/errata/RHSA-2021:2316
- https://access.redhat.com/errata/RHSA-2021:2314
- https://access.redhat.com/security/cve/cve-2020-27170
- http://packetstormsecurity.com/files/162117/Kernel-Live-Patch-Security-Notice-LSN-0075-1.html
- http://www.openwall.com/lists/oss-security/2021/03/24/4
- https://cdn.kernel.org/pub/linux/kernel/v5.x/ChangeLog-5.11.8
- https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=f232326f6966cf2a1d1db7bc917a4ce5f9f55f76
- https://lists.debian.org/debian-lts-announce/2021/03/msg00035.html
- https://lists.fedoraproject.org/archives/list/package-announce@lists.fedoraproject.org/message/FB6LUXPEIRLZH32YXWZVEZAD4ZL6SDK2/
- https://lists.fedoraproject.org/archives/list/package-announce@lists.fedoraproject.org/message/QRTPQE73ANG7D6M4L4PK5ZQDPO4Y2FVD/
- https://lists.fedoraproject.org/archives/list/package-announce@lists.fedoraproject.org/message/T2S3I4SLRNRUQDOFYUS6IUAZMQNMPNLG/
- https://www.openwall.com/lists/oss-security/2021/03/19/2
- https://launchpad.net/bugs/cve/CVE-2020-27170
- https://git.kernel.org/pub/scm/linux/kernel/git/bpf/bpf.git/patch/?id=f232326f6966cf2a1d1db7bc917a4ce5f9f55f76
- https://git.kernel.org/pub/scm/linux/kernel/git/bpf/bpf.git/patch/?id=10d2bb2e6b1d8c4576c56a748f697dbeb8388899
- https://git.kernel.org/pub/scm/linux/kernel/git/bpf/bpf.git/patch/?id=b5871dca250cd391885218b99cc015aca1a51aea
- https://git.kernel.org/pub/scm/linux/kernel/git/bpf/bpf.git/patch/?id=1b1597e64e1a610c7a96710fc4717158e98a08b3
- https://git.kernel.org/pub/scm/linux/kernel/git/bpf/bpf.git/patch/?id=0a13e3537ea67452d549a6a80da3776d6b7dedb3
- https://bugzilla.redhat.com/show_bug.cgi/show_bug.cgi?id=1940839
- https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/FB6LUXPEIRLZH32YXWZVEZAD4ZL6SDK2/
- https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/QRTPQE73ANG7D6M4L4PK5ZQDPO4Y2FVD/
- https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/T2S3I4SLRNRUQDOFYUS6IUAZMQNMPNLG/
- https://exchange.xforce.ibmcloud.com/vulnerabilities/198453
- https://www.ibm.com/support/pages/node/6497499 (Advisory)
- https://security-tracker.debian.org/tracker/CVE-2020-27170
- https://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2020-27170
- https://nvd.nist.gov/vuln/detail/CVE-2020-27170
- https://ubuntu.com/security/CVE-2020-27170
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