Linux: Use After Free
CVE-2023-53111 is a high-severity use after free vulnerability in Linux, with a CVSS 3.1 base score of 7.8 out of 10. It can be exploited with local access to the system by an attacker with a low-privileged account, without any action from a user. The record lists versions 81bf9d78fa246a166619196ff5005430ed2bc7c2, 407badf73ec9fb0d5744bf2ca1745c1818aa222f, e3fda704903f6d1fc351412f1bc6620333959ada as the first without the flaw, so updating Linux to one of those releases or later removes the exposure. There is no confirmed exploitation so far. EPSS estimates a 0.21% chance of exploitation within 30 days, which is low compared with other CVEs.
High severity with no evidence of exploitation so far.
What to do
- Update Linux to 81bf9d78fa246a166619196ff5005430ed2bc7c2 or 407badf73ec9fb0d5744bf2ca1745c1818aa222f or e3fda704903f6d1fc351412f1bc6620333959ada or 6917395c4667cfb607ed8bf1826205a59414657c, whichever matches your release line, or a later version.
- Update Linux Kernel to 5.15.104 or 6.1.21 or 6.2.8, whichever matches your release line, or a later version.
Affected products and versions
| Vendor | Product | Affected versions | Fixed in |
|---|---|---|---|
| Linux | Linux | bc07c10a3603a5ab3ef01ba42b3d41f9ac63d1b6 up to, but not including, 81bf9d78fa246a166619196ff5005430ed2bc7c2; bc07c10a3603a5ab3ef01ba42b3d41f9ac63d1b6 up to, but not including, 407badf73ec9fb0d5744bf2ca1745c1818aa222f; bc07c10a3603a5ab3ef01ba42b3d41f9ac63d1b6 up to, but not including, e3fda704903f6d1fc351412f1bc6620333959ada; bc07c10a3603a5ab3ef01ba42b3d41f9ac63d1b6 up to, but not including, 6917395c4667cfb607ed8bf1826205a59414657c; bc07c10a3603a5ab3ef01ba42b3d41f9ac63d1b6 up to, but not including, 9b0cb770f5d7b1ff40bea7ca385438ee94570eec; 4.4 | 81bf9d78fa246a166619196ff5005430ed2bc7c2, 407badf73ec9fb0d5744bf2ca1745c1818aa222f, e3fda704903f6d1fc351412f1bc6620333959ada, 6917395c4667cfb607ed8bf1826205a59414657c, 9b0cb770f5d7b1ff40bea7ca385438ee94570eec |
| Linux | Linux Kernel | 4.4 up to, but not including, 5.15.104; 5.16 up to, but not including, 6.1.21; 6.2 up to, but not including, 6.2.8; 6.3 | 5.15.104, 6.1.21, 6.2.8 |
Version data comes from the organisation that assigned the CVE. Confirm against the vendor advisory before deciding you are unaffected.
How the severity score breaks down
- Attack vector
- LocalThe attacker needs local access or must trick a user into running something.
- Attack complexity
- LowNo special conditions are needed; the attack works reliably.
- Privileges required
- LowA basic user account is enough.
- User interaction
- NoneNo action by a victim is required.
- Scope
- UnchangedImpact stays within the vulnerable component.
- Confidentiality
- HighAll data handled by the component can be read.
- Integrity
- HighData or code can be modified at will.
- Availability
- HighThe component can be taken down completely.
Vector: CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H. Scored by NVD.
| Scoring system | Score | Severity | Scored by |
|---|---|---|---|
| CVSS 3.1 | 7.8 | High | CNA |
| CVSS 3.1 | 7.8 | High | NVD |
Official description
In the Linux kernel, the following vulnerability has been resolved: loop: Fix use-after-free issues do_req_filebacked() calls blk_mq_complete_request() synchronously or asynchronously when using asynchronous I/O unless memory allocation fails. Hence, modify loop_handle_cmd() such that it does not dereference 'cmd' nor 'rq' after do_req_filebacked() finished unless we are sure that the request has not yet been completed. This patch fixes the following kernel crash: Unable to handle kernel NULL pointer dereference at virtual address 0000000000000054 Call trace: css_put.42938+0x1c/0x1ac loop_process_work+0xc8c/0xfd4 loop_rootcg_workfn+0x24/0x34 process_one_work+0x244/0x558 worker_thread+0x400/0x8fc kthread+0x16c/0x1e0 ret_from_fork+0x10/0x20
Source: the CVE record as published by its numbering authority, via NVD and CVE.org.
The underlying weakness: Use After Free
The product reuses or references memory after it has been freed. At some point afterward, the memory may be allocated again and saved in another pointer, while the original pointer references a location somewhere within the new allocation. Any operations using the original pointer are no longer valid because the memory belongs to the code that operates on the new pointer.
How developers prevent this class of flaw
- Choose a language that provides automatic memory management.
- When freeing pointers, be sure to set them to NULL once they are freed. However, the utilization of multiple or complex data structures may lower the usefulness of this strategy.
Timeline
- CVE record published.
- CISA published its SSVC assessment (exploitation: none, automatable: no, technical impact: total).
- Record last changed materially (score, affected products, status or references).
References
Patches and release notes
Other references
Recent Use After Free vulnerabilities
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- 7.8 High severity
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