Linux: Use After Free
CVE-2022-50422 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 117331a2a5227fb4369c2a1f321d3e3e2e2ef8fe, a9e5176ead6de64f572ad5c87a72825d9d3c82ae, e45a1516d2933703a4823d9db71e17c3abeba24f 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 0.16% 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 117331a2a5227fb4369c2a1f321d3e3e2e2ef8fe or a9e5176ead6de64f572ad5c87a72825d9d3c82ae or e45a1516d2933703a4823d9db71e17c3abeba24f or f7a785177611ffc97d645fcbc196e6de6ad2421d, whichever matches your release line, or a later version.
- Update Linux Kernel to 5.4.220 or 5.10.150 or 5.15.75 or 5.19.17, whichever matches your release line, or a later version.
Affected products and versions
| Vendor | Product | Affected versions | Fixed in |
|---|---|---|---|
| Linux | Linux | 2908d778ab3e244900c310974e1fc1c69066e450 up to, but not including, 117331a2a5227fb4369c2a1f321d3e3e2e2ef8fe; 2908d778ab3e244900c310974e1fc1c69066e450 up to, but not including, a9e5176ead6de64f572ad5c87a72825d9d3c82ae; 2908d778ab3e244900c310974e1fc1c69066e450 up to, but not including, e45a1516d2933703a4823d9db71e17c3abeba24f; 2908d778ab3e244900c310974e1fc1c69066e450 up to, but not including, f7a785177611ffc97d645fcbc196e6de6ad2421d; 2908d778ab3e244900c310974e1fc1c69066e450 up to, but not including, 2e12ce270f0d926085c1209cc90397e307deef97; 2908d778ab3e244900c310974e1fc1c69066e450 up to, but not including, 46ba53c30666717cb06c2b3c5d896301cd00d0c0; 2.6.19 | 117331a2a5227fb4369c2a1f321d3e3e2e2ef8fe, a9e5176ead6de64f572ad5c87a72825d9d3c82ae, e45a1516d2933703a4823d9db71e17c3abeba24f, f7a785177611ffc97d645fcbc196e6de6ad2421d, 2e12ce270f0d926085c1209cc90397e307deef97, 46ba53c30666717cb06c2b3c5d896301cd00d0c0 |
| Linux | Linux Kernel | 2.6.19 up to, but not including, 5.4.220; 5.5 up to, but not including, 5.10.150; 5.11 up to, but not including, 5.15.75; 5.16 up to, but not including, 5.19.17; 6.0 up to, but not including, 6.0.3 | 5.4.220, 5.10.150, 5.15.75, 5.19.17, 6.0.3 |
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 | NVD |
| CVSS 3.1 | 7.8 | High | CISA (ADP) |
Official description
In the Linux kernel, the following vulnerability has been resolved: scsi: libsas: Fix use-after-free bug in smp_execute_task_sg() When executing SMP task failed, the smp_execute_task_sg() calls del_timer() to delete "slow_task->timer". However, if the timer handler sas_task_internal_timedout() is running, the del_timer() in smp_execute_task_sg() will not stop it and a UAF will happen. The process is shown below: (thread 1) | (thread 2) smp_execute_task_sg() | sas_task_internal_timedout() ... | del_timer() | ... | ... sas_free_task(task) | kfree(task->slow_task) //FREE| | task->slow_task->... //USE Fix by calling del_timer_sync() in smp_execute_task_sg(), which makes sure the timer handler have finished before the "task->slow_task" is deallocated.
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
- git.kernel.org/stable/c/117331a2a5227fb4369c2a1f321d3e3e2e2ef8fe
- git.kernel.org/stable/c/2e12ce270f0d926085c1209cc90397e307deef97
- git.kernel.org/stable/c/46ba53c30666717cb06c2b3c5d896301cd00d0c0
- git.kernel.org/stable/c/a9e5176ead6de64f572ad5c87a72825d9d3c82ae
- git.kernel.org/stable/c/e45a1516d2933703a4823d9db71e17c3abeba24f
- git.kernel.org/stable/c/f7a785177611ffc97d645fcbc196e6de6ad2421d
Recent Use After Free vulnerabilities
- 8.1 High severity
- 7.8 High severity
- 7.8 High severity
- 7.8 High severity
- 7.8 High severity
- 7.8 High severity
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