CVE-2020-5955

Privilege escalation via uncontrolled software SMI input

Published Nov 3, 2021 · Updated Aug 4, 2024

Privilege escalation in Insyde InsydeH2O before 2021-10-14 allows attackers to gain elevated privileges via a software SMI call. The Int15MicrosoftSmm driver passes uncontrolled caller input to a software SMI function instead of validating it before privileged firmware processing. Exploitation requires the ability to invoke that SMI interface, and successful use elevates the caller's privileges on an affected Intel chipset.

CVSS severity9.8
Critical
EPSS probability1.41%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Privilege escalation in Insyde InsydeH2O before 2021-10-14 allows attackers to gain elevated privileges via a software SMI call. The Int15MicrosoftSmm driver passes uncontrolled caller input to a software SMI function instead of validating it before privileged firmware processing. Exploitation requires the ability to invoke that SMI interface, and successful use elevates the caller's privileges on an affected Intel chipset.

The record

CVE
CVE-2020-5955
Published
Nov 3, 2021
Updated
Aug 4, 2024
Vendor
Unknown vendor
Product
Unknown product
Classifications
T1068
Attack vector
Unavailable
Privileges
Unavailable

Timeline

How it unfolded

  1. Nov 3, 2021CVE publishedPublication date reported by the CVE source.
  2. Aug 4, 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 vectorUnavailable in this record.
Required privilegesUnavailable in this record.

What is affected?

Affected products and versions are unavailable in this record.

Published CVSS scores

7.5NIST NVDAV:N/AC:L/Au:N/C:P/I:P/A:P
9.8NIST NVDCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/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.

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No observations available

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

Weakness, pattern, technique

T1068Exploitation for Privilege Escalation

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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