Local privilege escalation via missing file reference
Published Feb 23, 2021 · Updated Aug 3, 2024
Use-after-free in Linux Kernel 5.6 through 5.7 allows local users to escalate privileges or crash the system through io_uring. The io_grab_files() path for IORING_OP_CLOSE passes files_struct to a kernel worker without taking a reference, permitting access after it is freed. Exploitation requires local low-privileged code and a race; the published technique is limited to a single-core environment and enables arbitrary kernel-memory read and write.
Summary
What happened
Use-after-free in Linux Kernel 5.6 through 5.7 allows local users to escalate privileges or crash the system through io_uring. The io_grab_files() path for IORING_OP_CLOSE passes files_struct to a kernel worker without taking a reference, permitting access after it is freed. Exploitation requires local low-privileged code and a race; the published technique is limited to a single-core environment and enables arbitrary kernel-memory read and write.
The record
- CVE
- CVE-2021-20226
- Published
- Feb 23, 2021
- Updated
- Aug 3, 2024
- Vendor
- The Linux Kernel Organization
- Product
- Linux Kernel
- Classifications
- CWE-416, T1068
- Attack vector
- local
- Privileges
- authenticated
Timeline
How it unfolded
- Feb 23, 2021CVE 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
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Is a vulnerable build present?
Compare these published version ranges with your installed build and any vendor patches.
- Affected versionversion=kernel 5.10
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
- ZDI io_uring reference-counting exploit methodfunctional · demonstrated
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Technologies
Your stack
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Your stack
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