Linux: Use After Free
CVE-2023-52837 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 4e9b3ec84dc97909876641dad14e0a2300d6c2a3, 879947f4180bc6e83af64eb0515e0cf57fce15db, 56bd7901b5e9dbc9112036ea615ebcba1565fafe 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 0.25% 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 4e9b3ec84dc97909876641dad14e0a2300d6c2a3 or 879947f4180bc6e83af64eb0515e0cf57fce15db or 56bd7901b5e9dbc9112036ea615ebcba1565fafe or 327462725b0f759f093788dfbcb2f1fd132f956b, whichever matches your release line, or a later version.
- Update Linux Kernel to 6.1.63 or 6.5.12 or 6.6.2, whichever matches your release line, or a later version.
Affected products and versions
| Vendor | Product | Affected versions | Fixed in |
|---|---|---|---|
| Linux | Linux | 4af5f2e0301311f88c420fcfc5f3c8611ade20ac up to, but not including, 4e9b3ec84dc97909876641dad14e0a2300d6c2a3; 4af5f2e0301311f88c420fcfc5f3c8611ade20ac up to, but not including, 879947f4180bc6e83af64eb0515e0cf57fce15db; 4af5f2e0301311f88c420fcfc5f3c8611ade20ac up to, but not including, 56bd7901b5e9dbc9112036ea615ebcba1565fafe; 4af5f2e0301311f88c420fcfc5f3c8611ade20ac up to, but not including, 327462725b0f759f093788dfbcb2f1fd132f956b; 5.14 | 4e9b3ec84dc97909876641dad14e0a2300d6c2a3, 879947f4180bc6e83af64eb0515e0cf57fce15db, 56bd7901b5e9dbc9112036ea615ebcba1565fafe, 327462725b0f759f093788dfbcb2f1fd132f956b |
| Linux | Linux Kernel | 5.14 up to, but not including, 6.1.63; 6.2 up to, but not including, 6.5.12; 6.6 up to, but not including, 6.6.2 | 6.1.63, 6.5.12, 6.6.2 |
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: nbd: fix uaf in nbd_open Commit 4af5f2e03013 ("nbd: use blk_mq_alloc_disk and blk_cleanup_disk") cleans up disk by blk_cleanup_disk() and it won't set disk->private_data as NULL as before. UAF may be triggered in nbd_open() if someone tries to open nbd device right after nbd_put() since nbd has been free in nbd_dev_remove(). Fix this by implementing ->free_disk and free private data in it.
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: partial).
- Record last changed materially (score, affected products, status or references).
References
Patches and release notes
Recent Use After Free vulnerabilities
- 7.8 High severity
- 7.8 High severity
- 7.8 High severity
- 7.8 High severity
- 7.8 High severity
- 8.8 High severity
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