CVE-2021-26401

Local memory disclosure via insufficient LFENCE/JMP serialization

Published Mar 11, 2022 · Updated Sep 17, 2024

Speculative-execution exposure in AMD processors allows local users to infer host memory through a flawed LFENCE/JMP mitigation. The V2-2 LFENCE/JMP sequence leaves a speculative-execution window large enough for branch-target injection despite the intended fence. A local low-privileged context and an affected CPU using this mitigation are required; successful exploitation discloses host memory, including data assigned to other guests.

CVSS severity5.6
Medium
EPSS probability0.29%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Speculative-execution exposure in AMD processors allows local users to infer host memory through a flawed LFENCE/JMP mitigation. The V2-2 LFENCE/JMP sequence leaves a speculative-execution window large enough for branch-target injection despite the intended fence. A local low-privileged context and an affected CPU using this mitigation are required; successful exploitation discloses host memory, including data assigned to other guests.

The record

CVE
CVE-2021-26401
Published
Mar 11, 2022
Updated
Sep 17, 2024
Vendor
Unknown vendor
Product
Unknown product
Classifications
Unavailable
Attack vector
local
Privileges
authenticated

Timeline

How it unfolded

  1. Mar 11, 2022CVE publishedPublication date reported by the CVE source.
  2. Sep 17, 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

1.9NIST NVDAV:L/AC:M/Au:N/C:P/I:N/A:N
5.6NIST NVDCVSS:3.1/AV:L/AC:H/PR:L/UI:N/S:C/C:H/I:N/A:N
4.7Oracle LinuxCVSS:3.0/AV:L/AC:H/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

No sourced classifications are available.

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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