CVE-2020-27171

Severity: medium (CVSS 6.0 v3.1)
Exploited in the wild: not listed in CISA KEV
EPSS: 0.6% probability of exploitation in the next 30 days
Public exploit or detection template: none known
Published: 2021-03-20 · updated 2026-10-08
Weakness: CWE-193

Description

An issue was discovered in the Linux kernel before 5.11.8. kernel/bpf/verifier.c has an off-by-one error (with a resultant integer underflow) affecting out-of-bounds speculation on pointer arithmetic, leading to side-channel attacks that defeat Spectre mitigations and obtain sensitive information from kernel memory, aka CID-10d2bb2e6b1d.

Affected products

Canonical Ubuntu Linux: 14.04, 16.04, 18.04, 20.04
Debian Linux: 9.0
Fedoraproject Fedora: 32, 33, 34
Linux kernel: before 5.11.8 — fixed in 5.11.8

How to fix

Upgrade to a fixed version: Linux kernel 5.11.8. Check the vendor advisory for mitigations.

References

http://packetstormsecurity.com/files/162117/Kernel-Live-Patch-Security-Notice-LSN-0075-1.html
http://www.openwall.com/lists/oss-security/2021/03/24/5
https://cdn.kernel.org/pub/linux/kernel/v5.x/ChangeLog-5.11.8
https://git.kernel.org/pub/scm/linux/kernel/git/bpf/bpf.git/patch/?id=10d2bb2e6b1d8c4576c56a748f697dbeb8388899
https://lists.debian.org/debian-lts-announce/2021/03/msg00035.html
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://www.openwall.com/lists/oss-security/2021/03/19/3
http://packetstormsecurity.com/files/162117/Kernel-Live-Patch-Security-Notice-LSN-0075-1.html
http://www.openwall.com/lists/oss-security/2021/03/24/5
https://cdn.kernel.org/pub/linux/kernel/v5.x/ChangeLog-5.11.8

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