CVE-2021-41073
📋 TL;DR
This is a local privilege escalation vulnerability in the Linux kernel's io_uring subsystem. It allows local users to trigger a use-after-free condition by exploiting the IORING_OP_PROVIDE_BUFFERS operation, potentially gaining root privileges. Affects Linux kernel versions 5.10 through 5.14.6.
💻 Affected Systems
- Linux kernel
📦 What is this software?
Fedora by Fedoraproject
Fedora by Fedoraproject
Linux Kernel by Linux
The Linux Kernel is the core component of the Linux operating system, serving as the critical interface between computer hardware and software processes. As the heart of millions of servers, cloud infrastructure, embedded systems, Android devices, and IoT deployments worldwide, the Linux Kernel mana...
Learn more about Linux Kernel →Linux Kernel by Linux
The Linux Kernel is the core component of the Linux operating system, serving as the critical interface between computer hardware and software processes. As the heart of millions of servers, cloud infrastructure, embedded systems, Android devices, and IoT deployments worldwide, the Linux Kernel mana...
Learn more about Linux Kernel →⚠️ Risk & Real-World Impact
Worst Case
Local attacker gains full root privileges, compromising the entire system and potentially accessing sensitive data or installing persistent malware.
Likely Case
Local user escalates privileges to root, enabling unauthorized access to system resources and data.
If Mitigated
With proper access controls limiting local user accounts, impact is reduced but still significant for authorized users.
🎯 Exploit Status
Exploit requires local user access and knowledge of the vulnerability. Public exploit code exists in security mailing lists.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: Linux kernel 5.14.7 and later, backported to stable kernels
Vendor Advisory: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=16c8d2df7ec0eed31b7d3b61cb13206a7fb930cc
Restart Required: Yes
Instructions:
1. Update Linux kernel to version 5.14.7 or later. 2. For distributions with backported patches, apply security updates from your vendor. 3. Reboot the system to load the new kernel.
🔧 Temporary Workarounds
Disable io_uring module
linuxPrevent loading of the vulnerable io_uring kernel module
echo 'blacklist io_uring' >> /etc/modprobe.d/blacklist.conf
rmmod io_uring
Restrict local user access
linuxLimit which users have shell access to vulnerable systems
🧯 If You Can't Patch
- Implement strict access controls to limit local user accounts
- Monitor for privilege escalation attempts and unusual root activity
🔍 How to Verify
Check if Vulnerable:
Check kernel version with 'uname -r' and compare to affected range 5.10-5.14.6Check Version:
uname -rVerify Fix Applied:
Verify kernel version is 5.14.7 or later, or check with distribution-specific security update verification📡 Detection & Monitoring
Log Indicators:
- Unusual privilege escalation events in audit logs
- Failed attempts to load io_uring module
- Suspicious process creation with elevated privileges
Network Indicators:
- Not applicable - local exploit only
SIEM Query:
search 'privilege escalation' OR 'setuid' OR 'setgid' in process execution logs from non-root users🔗 References
- http://www.openwall.com/lists/oss-security/2021/09/18/2
- http://www.openwall.com/lists/oss-security/2021/09/18/2
- http://www.openwall.com/lists/oss-security/2022/06/04/4
- https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=16c8d2df7ec0eed31b7d3b61cb13206a7fb930cc
- https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/J7KSMIOQ4377CVTHMWNGNCWHMCRFRP2T/
- https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/PAP4TXEZ7J4EZQMQW5SIJMWXG7WZT3F7/
- https://security.netapp.com/advisory/ntap-20211014-0003/
- https://www.debian.org/security/2021/dsa-4978
- http://www.openwall.com/lists/oss-security/2021/09/18/2
- http://www.openwall.com/lists/oss-security/2021/09/18/2
- http://www.openwall.com/lists/oss-security/2022/06/04/4
- https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=16c8d2df7ec0eed31b7d3b61cb13206a7fb930cc
- https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/J7KSMIOQ4377CVTHMWNGNCWHMCRFRP2T/
- https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/PAP4TXEZ7J4EZQMQW5SIJMWXG7WZT3F7/
- https://security.netapp.com/advisory/ntap-20211014-0003/
- https://www.debian.org/security/2021/dsa-4978
