CVE-2021-47277

Guest-to-host memory disclosure via speculative address translation

Published May 21, 2024 · Updated May 11, 2026

Speculative address translation in Linux KVM allows guest OS users to form a gadget that reads VMM process memory via invalid guest addresses. __gfn_to_hva_memslot speculatively computes an out-of-bounds host virtual address after a bounds check on an invalid guest frame number is mispredicted, creating a data-dependent two-read gadget. ARM address masking exposes the reported path, while x86 LFENCE blocks it, and no exploitable case has been demonstrated.

CVSS severity7.1
High
EPSS probability0.26%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Speculative address translation in Linux KVM allows guest OS users to form a gadget that reads VMM process memory via invalid guest addresses. __gfn_to_hva_memslot speculatively computes an out-of-bounds host virtual address after a bounds check on an invalid guest frame number is mispredicted, creating a data-dependent two-read gadget. ARM address masking exposes the reported path, while x86 LFENCE blocks it, and no exploitable case has been demonstrated.

The record

CVE
CVE-2021-47277
Published
May 21, 2024
Updated
May 11, 2026
Vendor
The Linux Kernel Organization
Product
Linux
Classifications
Unavailable
Attack vector
local
Privileges
authenticated

Timeline

How it unfolded

  1. May 21, 2024CVE publishedPublication date reported by the CVE source.
  2. May 11, 2026Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

Compare your product and version with the public record. A matching version still requires validation against your environment.

Is a vulnerable build present?

Compare these published version ranges with your installed build and any vendor patches.

  1. Affected versionversion=2.6.25
  2. Affected versionversion=8a7ae055f3533b520401c170ac55e30628b34df5 <22b87fb17a28d37331bb9c1110737627b17f6781
  3. Affected versionversion=8a7ae055f3533b520401c170ac55e30628b34df5 <3098b86390a6b9ea52657689f08410baf130ceff
  4. Affected versionversion=8a7ae055f3533b520401c170ac55e30628b34df5 <361ce3b917aff93123e9e966d8608655c967f438
  5. Affected versionversion=8a7ae055f3533b520401c170ac55e30628b34df5 <740621309b25bbf619b8a0ba5fd50a8e58989441
  6. Affected versionversion=8a7ae055f3533b520401c170ac55e30628b34df5 <7af299b97734c7e7f465b42a2139ce4d77246975
  7. Affected versionversion=8a7ae055f3533b520401c170ac55e30628b34df5 <bff1fbf0cf0712686f1df59a83fba6e31d2746a0
  8. Affected versionversion=8a7ae055f3533b520401c170ac55e30628b34df5 <da27a83fd6cc7780fea190e1f5c19e87019da65c
  9. Affected versionversion=8a7ae055f3533b520401c170ac55e30628b34df5 <ed0e2a893092c7fcb4ff7ba74e5efce53a6f5940

What conditions does exploitation require?

Attack vectorlocal
Required privilegesauthenticated

What is affected?

The Linux Kernel Organization · Linuxversion=2.6.25; version=8a7ae055f3533b520401c170ac55e30628b34df5 <22b87fb17a28d37331bb9c1110737627b17f6781; version=8a7ae055f3533b520401c170ac55e30628b34df5 <3098b86390a6b9ea52657689f08410baf130ceff; version=8a7ae055f3533b520401c170ac55e30628b34df5 <361ce3b917aff93123e9e966d8608655c967f438; version=8a7ae055f3533b520401c170ac55e30628b34df5 <740621309b25bbf619b8a0ba5fd50a8e58989441; version=8a7ae055f3533b520401c170ac55e30628b34df5 <7af299b97734c7e7f465b42a2139ce4d77246975; version=8a7ae055f3533b520401c170ac55e30628b34df5 <bff1fbf0cf0712686f1df59a83fba6e31d2746a0; version=8a7ae055f3533b520401c170ac55e30628b34df5 <da27a83fd6cc7780fea190e1f5c19e87019da65c; version=8a7ae055f3533b520401c170ac55e30628b34df5 <ed0e2a893092c7fcb4ff7ba74e5efce53a6f5940

Published CVSS scores

7.1CanonicalCVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:N/A:H

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 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 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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