CVE-2022-49694
Published: 26 February 2025
Summary
CVE-2022-49694 is a high-severity Use After Free (CWE-416) vulnerability in Linux Linux Kernel. Its CVSS base score is 7.8 (High).
Operationally, exploitation aligns with the MITRE ATT&CK technique Exploitation for Privilege Escalation (T1068); ranked at the 28.7th percentile by exploit likelihood (below the median); it is not currently listed in the CISA KEV catalog.
The strongest mitigations our analysis identified are NIST 800-53 RA-5 (Vulnerability Monitoring and Scanning) and SI-2 (Flaw Remediation).
Deeper analysis
CVE-2022-49694 is a use-after-free vulnerability (CWE-416) in the Linux kernel's block layer, specifically affecting the elevator interface during disk teardown operations. The issue arises because the elevator disabling and scheduler tag freeing occur in disk_release and blk_cleanup_queue, potentially leading to a use-after-free of q->tag_set when it is no longer valid. This is resolved by moving these operations, along with blk_qos_exit, to the end of del_gendisk to ensure they happen after filesystem requests are stopped and the queue is properly frozen.
A local attacker with low privileges (PR:L) can exploit this vulnerability with low attack complexity (AC:L) and no user interaction required (UI:N), in a local attack vector (AV:L) with unchanged scope (S:U). Successful exploitation can result in high impacts to confidentiality, integrity, and availability (C:H/I:H/A:H), as scored at CVSS 7.8 (CVSS:3.1), potentially allowing arbitrary code execution or system crashes during block device removal.
The provided patch references detail the mitigation: commit 50e34d78815e474d410f342fbe783b18192ca518 and commit f28699fafc047ec33299da01e928c3a0073c5cc6 in the Linux kernel stable tree move the elevator exit, tag_set freeing, and blk_qos_exit to del_gendisk, preventing the use-after-free by ensuring these steps occur after queue freeze and filesystem request cessation. Security practitioners should apply these stable kernel updates to affected systems.
EU & UK References
- 🇪🇺 ENISA EUVD: EUVD-2022-54541
Vulnerability details
In the Linux kernel, the following vulnerability has been resolved: block: disable the elevator int del_gendisk The elevator is only used for file system requests, which are stopped in del_gendisk. Move disabling the elevator and freeing the scheduler tags to…
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the end of del_gendisk instead of doing that work in disk_release and blk_cleanup_queue to avoid a use after free on q->tag_set from disk_release as the tag_set might not be alive at that point. Move the blk_qos_exit call as well, as it just depends on the elevator exit and would be the only reason to keep the not exactly cheap queue freeze in disk_release.
- CWE(s)
Related Threats
MITRE ATT&CK Enterprise TechniquesAI
Why these techniques?
Local kernel UAF in block layer directly enables privilege escalation via arbitrary code execution from low-privileged context.
CVEs Like This One
Affected Assets
Mitigating Controls
Mitigating Controls (NIST 800-53 r5) AI
Mandates timely identification, reporting, and patching of flaws like the use-after-free in the Linux kernel block layer elevator during disk teardown.
Requires vulnerability scanning and monitoring to identify systems running kernel versions affected by CVE-2022-49694.
Provides memory protections such as DEP and ASLR that mitigate exploitation of the use-after-free vulnerability by preventing unauthorized code execution.