Arbitrary SMM code execution via unchecked buffer address
Published Apr 22, 2022 · Updated Aug 3, 2024
Improper input validation in Lenovo Notebook BIOS on affected models allows local users with elevated privileges to execute arbitrary SMM code. The LenovoVariableSmm software SMI handler passes a caller-controlled physical buffer address directly to LenovoVariable read and write operations without checking whether it overlaps SMRAM. A privileged kernel-mode process can use crafted buffers to read or overwrite SMRAM, gaining SMM execution and a path to a persistent firmware implant.
Summary
What happened
Improper input validation in Lenovo Notebook BIOS on affected models allows local users with elevated privileges to execute arbitrary SMM code. The LenovoVariableSmm software SMI handler passes a caller-controlled physical buffer address directly to LenovoVariable read and write operations without checking whether it overlaps SMRAM. A privileged kernel-mode process can use crafted buffers to read or overwrite SMRAM, gaining SMM execution and a path to a persistent firmware implant.
The record
- CVE
- CVE-2021-3970
- Published
- Apr 22, 2022
- Updated
- Aug 3, 2024
- Vendor
- Lenovo
- Product
- Notebook BIOS
- Classifications
- CWE-20, T1542.001
- Attack vector
- local
- Privileges
- admin
Timeline
How it unfolded
- Apr 22, 2022CVE publishedPublication date reported by the CVE source.
- Aug 3, 2024Record 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.
- Affected versionversion=various
What conditions does exploitation require?
What is affected?
Published CVSS scores
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.
Public exploit references
- CHIPSEC SMRAM read proof of conceptproof of concept · demonstrated
Labels summarize the accepted research assessment. They do not indicate a test against your environment.
Technologies
Your stack
See the directory against your own environment.
Your stack
Check the software in your environment
Book a demo to see how Hinoki identifies affected software and validates exploitability in your environment.
Book a demo