Local privilege escalation via linked-timeout double release
Published Mar 15, 2024 · Updated Aug 5, 2026
Use-after-free in the Linux kernel io_uring subsystem allows local users to gain kernel privileges through linked-timeout requests. A race lets master completion call io_req_complete() before io_link_timeout_fn() calls io_put_req_deferred(), dropping two references to one request and reusing the freed io_kiocb. An unprivileged account controls both sides through local io_uring syscalls; exploitation can modify kernel memory or crash the host.
Summary
What happened
Use-after-free in the Linux kernel io_uring subsystem allows local users to gain kernel privileges through linked-timeout requests. A race lets master completion call io_req_complete() before io_link_timeout_fn() calls io_put_req_deferred(), dropping two references to one request and reusing the freed io_kiocb. An unprivileged account controls both sides through local io_uring syscalls; exploitation can modify kernel memory or crash the host.
The record
- CVE
- CVE-2021-47124
- Published
- Mar 15, 2024
- Updated
- Aug 5, 2026
- Vendor
- The Linux Kernel Organization
- Product
- Linux
- Classifications
- T1068
- Attack vector
- local
- Privileges
- authenticated
Timeline
How it unfolded
- Mar 15, 2024CVE publishedPublication date reported by the CVE source.
- Aug 5, 2026Record 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=1c20e9040f49687ba2ccc2ffd4411351a6c2ebff <0b2a990e5d2f76d020cb840c456e6ec5f0c27530
- Affected versionversion=1c20e9040f49687ba2ccc2ffd4411351a6c2ebff <6f5d7a45f58d3abe3a936de1441b8d6318f978ff
- Affected versionversion=5.10.26 <5.10.43
- Affected versionversion=5.10.26 <5.10.55
- Affected versionversion=5.11.6 <5.12
- Affected versionversion=5.12
- Affected versionversion=567c81912cec641db75ac6cb64c63f8367c97d19
- Affected versionversion=9ae1f8dd372e0e4c020b345cf9e09f519265e981 <876808dba2ff7509bdd7f230c4f374a0caf4f410
- Affected versionversion=9ae1f8dd372e0e4c020b345cf9e09f519265e981 <a298232ee6b9a1d5d732aa497ff8be0d45b5bd82
- Affected versionversion=9ae1f8dd372e0e4c020b345cf9e09f519265e981 <ff4a96ba5c8f9b266706280ff8021d2ef3f17e86
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.
Weakness, pattern, technique
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
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