CVE-2021-38578

SMM privilege escalation via unchecked buffer subtraction

Published Mar 3, 2022 · Updated Nov 3, 2025

Buffer underflow in TianoCore EDK II edk2-stable202208 allows local users with high privileges to escalate into SMM. SmmEntryPoint subtracts the EFI_SMM_COMMUNICATE_HEADER Data offset from a user-controlled BufferSize without checking for unsigned underflow, then passes the wrapped size to SmiManage. Exploitation requires high local privileges and high-complexity control of a malformed communication-buffer size, permitting code or memory effects across the SMM boundary.

CVSS severity7.4
High
EPSS probability1.01%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Buffer underflow in TianoCore EDK II edk2-stable202208 allows local users with high privileges to escalate into SMM. SmmEntryPoint subtracts the EFI_SMM_COMMUNICATE_HEADER Data offset from a user-controlled BufferSize without checking for unsigned underflow, then passes the wrapped size to SmiManage. Exploitation requires high local privileges and high-complexity control of a malformed communication-buffer size, permitting code or memory effects across the SMM boundary.

The record

CVE
CVE-2021-38578
Published
Mar 3, 2022
Updated
Nov 3, 2025
Vendor
TianoCore
Product
EDK II
Classifications
CWE-124, T1068
Attack vector
local
Privileges
admin

Timeline

How it unfolded

  1. Mar 3, 2022CVE publishedPublication date reported by the CVE source.
  2. Nov 3, 2025Record 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=edk2-stable202208

What conditions does exploitation require?

Attack vectorlocal
Required privilegesadmin

What is affected?

TianoCore · EDK IIversion=edk2-stable202208

Published CVSS scores

7.4TianoCore.orgCVSS:3.1/AV:L/AC:H/PR:H/UI:N/S:C/C:H/I:H/A:L
7.5NVDAV:N/AC:L/Au:N/C:P/I:P/A:P
9.8NVDCVSS: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)
Vectorlocal
Privilegesadmin
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-124Buffer Underwrite ('Buffer Underflow')
T1068Exploitation for Privilege Escalation

Public exploit references

No public exploit references are available in this record.

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Technologies

Your stack

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Your stack

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