Linux: Use After Free
CVE-2023-52629 is a high-severity use after free vulnerability in Linux, with a CVSS 3.1 base score of 8.4 out of 10. It can be exploited with local access to the system by an unauthenticated attacker, without any action from a user. The record lists versions ff635d1f143b55fa005e9e43b16e6d8f677e90a5, 610dbd8ac271aa36080aac50b928d700ee3fe4de, 246f80a0b17f8f582b2c0996db02998239057c65 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 ff635d1f143b55fa005e9e43b16e6d8f677e90a5 or 610dbd8ac271aa36080aac50b928d700ee3fe4de or 246f80a0b17f8f582b2c0996db02998239057c65, whichever matches your release line, or a later version.
- Update linux_kernel to 610dbd8ac271 or 246f80a0b17f, whichever matches your release line, or a later version.
Affected products and versions
| Vendor | Product | Affected versions | Fixed in |
|---|---|---|---|
| Linux | Linux | 9f5e8eee5cfe1328660c71812d87c2a67bda389f up to, but not including, ff635d1f143b55fa005e9e43b16e6d8f677e90a5; 9f5e8eee5cfe1328660c71812d87c2a67bda389f up to, but not including, 610dbd8ac271aa36080aac50b928d700ee3fe4de; 9f5e8eee5cfe1328660c71812d87c2a67bda389f up to, but not including, 246f80a0b17f8f582b2c0996db02998239057c65; 2.6.20 | ff635d1f143b55fa005e9e43b16e6d8f677e90a5, 610dbd8ac271aa36080aac50b928d700ee3fe4de, 246f80a0b17f8f582b2c0996db02998239057c65 |
| Linux | linux_kernel | 9f5e8eee5cfe up to, but not including, 610dbd8ac271; 9f5e8eee5cfe up to, but not including, 246f80a0b17f; 2.6.20 | 610dbd8ac271, 246f80a0b17f |
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
- NoneNo account or login is needed.
- 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:N/UI:N/S:U/C:H/I:H/A:H. Scored by CISA (ADP).
Official description
In the Linux kernel, the following vulnerability has been resolved: sh: push-switch: Reorder cleanup operations to avoid use-after-free bug The original code puts flush_work() before timer_shutdown_sync() in switch_drv_remove(). Although we use flush_work() to stop the worker, it could be rescheduled in switch_timer(). As a result, a use-after-free bug can occur. The details are shown below: (cpu 0) | (cpu 1) switch_drv_remove() | flush_work() | ... | switch_timer // timer | schedule_work(&psw->work) timer_shutdown_sync() | ... | switch_work_handler // worker kfree(psw) // free | | psw->state = 0 // use This patch puts timer_shutdown_sync() before flush_work() to mitigate the bugs. As a result, the worker and timer will be stopped safely before the deallocate operations.
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
- 8.8 High severity
- 7.8 High severity
- 7.5 High severity
- 8.8 High severity
- 8.8 High severity
- 7.8 High severity
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