CVE-2021-28690

Cross-context memory disclosure via un-restored TSX controls

Published Jun 29, 2021 · Updated Aug 3, 2024

Information disclosure in Xen Hypervisor 4.11.x, 4.12.x, and 4.13.x allows guest OS users to sample memory after an S3 resume. The CPU0 S3 resume path reloads microcode but omits tsx_init, so the selected MSR_TSX_CTRL setting that disables TSX is not restored. Exposure requires a TAA-susceptible Intel x86 processor, the earlier TAA mitigation, S3 suspend and resume, and attacker execution on CPU0.

CVSS severity6.5
Medium
EPSS probability1.02%
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 Xen Hypervisor 4.11.x, 4.12.x, and 4.13.x allows guest OS users to sample memory after an S3 resume. The CPU0 S3 resume path reloads microcode but omits tsx_init, so the selected MSR_TSX_CTRL setting that disables TSX is not restored. Exposure requires a TAA-susceptible Intel x86 processor, the earlier TAA mitigation, S3 suspend and resume, and attacker execution on CPU0.

The record

CVE
CVE-2021-28690
Published
Jun 29, 2021
Updated
Aug 3, 2024
Vendor
Xen Project
Product
Xen Hypervisor
Classifications
Unavailable
Attack vector
local
Privileges
authenticated

Timeline

How it unfolded

  1. Jun 29, 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?

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

  1. Affected versionversion=4.11.x
  2. Affected versionversion=4.12.x
  3. Affected versionversion=4.13.x <unspecified

What conditions does exploitation require?

Attack vectorlocal
Required privilegesauthenticated

What is affected?

Xen Project · Xen Hypervisorversion=4.11.x; version=4.12.x; version=4.13.x <unspecified

Published CVSS scores

6.5National Vulnerability DatabaseCVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:N/A:N
4.0National Vulnerability DatabaseAV:N/AC:L/Au:S/C:P/I:N/A:N
6.5OracleCVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:N/A:N
5.6SUSECVSS:3.1/AV:L/AC:H/PR:L/UI:N/S:C/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 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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