CVE-2021-31829

Kernel-memory disclosure via speculative BPF stack loads

Published May 6, 2021 · Updated Aug 3, 2024

Information disclosure in the Linux kernel through 5.12.1 allows local users to read kernel stack data through a side channel. The BPF verifier's stack-pointer sanitization permits transient intermediate offsets to load unwritten stack slots containing residual kernel data. Loading an unprivileged BPF program is required; disclosed kernel addresses can weaken KASLR and facilitate exploitation of another flaw.

CVSS severity5.5
Medium
EPSS probability0.31%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Information disclosure in the Linux kernel through 5.12.1 allows local users to read kernel stack data through a side channel. The BPF verifier's stack-pointer sanitization permits transient intermediate offsets to load unwritten stack slots containing residual kernel data. Loading an unprivileged BPF program is required; disclosed kernel addresses can weaken KASLR and facilitate exploitation of another flaw.

The record

CVE
CVE-2021-31829
Published
May 6, 2021
Updated
Aug 3, 2024
Vendor
Unknown vendor
Product
Unknown product
Classifications
CWE-863
Attack vector
local
Privileges
authenticated

Timeline

How it unfolded

  1. May 6, 2021CVE publishedPublication date reported by the CVE source.
  2. Aug 3, 2024Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

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Is a vulnerable build present?

Affected buildAffected product and version details are unavailable.

What conditions does exploitation require?

Attack vectorlocal
Required privilegesauthenticated

What is affected?

Affected products and versions are unavailable in this record.

Published CVSS scores

6.2Amazon LinuxCVSS:3.1/AV:L/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N
5.5Canonical UbuntuCVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:N/A:N
5.5NIST NVDCVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:N/A:N

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

Daily unique IPsNo honeypot observations are available for this CVE in the selected window.

No observations available

Sep 10, 2026Sep 16, 2026
Latest reporting daySep 16, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectorlocal
Privilegesauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-863Incorrect Authorization

Public exploit references

No public exploit references are available in this record.

Labels summarize the accepted research assessment. They do not indicate a test against your environment.

Technologies

Your stack

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Your stack

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