Kernel privilege escalation via oversized USB control requests
Published Mar 16, 2022 · Updated Aug 4, 2024
Out-of-bounds write in the Linux Kernel USB gadget subsystem allows local users to gain kernel privileges through oversized USB requests. Affected setup handlers queue endpoint-zero transfers whose attacker-controlled wLength exceeds the 4,096-byte buffer, while the direction guard compares the full bRequestType field instead of its direction bit. Exploitation requires an affected USB gadget class and a connected host capable of sending crafted control transfers; successful writes permit kernel-context code execution or a kernel crash.
Summary
What happened
Out-of-bounds write in the Linux Kernel USB gadget subsystem allows local users to gain kernel privileges through oversized USB requests. Affected setup handlers queue endpoint-zero transfers whose attacker-controlled wLength exceeds the 4,096-byte buffer, while the direction guard compares the full bRequestType field instead of its direction bit. Exploitation requires an affected USB gadget class and a connected host capable of sending crafted control transfers; successful writes permit kernel-context code execution or a kernel crash.
The record
- CVE
- CVE-2021-39685
- Published
- Mar 16, 2022
- Updated
- Aug 4, 2024
- Vendor
- The Linux Kernel Organization
- Product
- Linux Kernel
- Classifications
- CWE-787, T1068
- Attack vector
- local
- Privileges
- authenticated
Timeline
How it unfolded
- Mar 16, 2022CVE publishedPublication date reported by the CVE source.
- 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?
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- Affected versionversion=Android kernel
What conditions does exploitation require?
What is affected?
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
- inspector-gadget USB gadget sample exploitfunctional · demonstrated
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Technologies
Your stack
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Your stack
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