CVE-2021-26318Public exploit

Kernel-address disclosure via PREFETCH timing variation

Published Oct 13, 2021 · Updated Sep 16, 2024

Timing side channel in AMD CPUs allows local users to disclose kernel address-space layout through x86 PREFETCH instructions. PREFETCH execution time varies with the page-table level at which a kernel-address walk aborts, and its timing also exposes TLB state. Unprivileged code can break KASLR locally, but AMD states that the attack does not directly disclose data across address-space boundaries.

CVSS severity4.7
Medium
EPSS probability0.33%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Timing side channel in AMD CPUs allows local users to disclose kernel address-space layout through x86 PREFETCH instructions. PREFETCH execution time varies with the page-table level at which a kernel-address walk aborts, and its timing also exposes TLB state. Unprivileged code can break KASLR locally, but AMD states that the attack does not directly disclose data across address-space boundaries.

The record

CVE
CVE-2021-26318
Published
Oct 13, 2021
Updated
Sep 16, 2024
Vendor
Unknown vendor
Product
Unknown product
Classifications
CWE-203, CWE-208
Attack vector
local
Privileges
authenticated

Timeline

How it unfolded

  1. Oct 13, 2021CVE publishedPublication date reported by the CVE source.
  2. Sep 16, 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

4.7NIST NVDCVSS:3.1/AV:L/AC:H/PR:L/UI:N/S:U/C:H/I:N/A:N
1.9NIST NVDAV:L/AC:M/Au:N/C:P/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.

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No observations available

Sep 9, 2026Sep 15, 2026
Latest reporting daySep 15, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectorlocal
Privilegesauthenticated
Known exploitationUnconfirmed
Public exploitPublished

Weakness, pattern, technique

CWE-203Observable Discrepancy
CWE-208Observable Timing Discrepancy

Public exploit references

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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