Linux: Use After Free
CVE-2023-53235 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 c9d8be0e533738b744abb669263c4750d4830009, 139a27854bf5ce93ff9805f9f7683b88c13074dc 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 0.17% 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 c9d8be0e533738b744abb669263c4750d4830009 or 139a27854bf5ce93ff9805f9f7683b88c13074dc, whichever matches your release line, or a later version.
- Update Linux Kernel to 6.5.5 or a later version.
Affected products and versions
| Vendor | Product | Affected versions | Fixed in |
|---|---|---|---|
| Linux | Linux | d98780310719bf4076d975c2ff65c44c7c0d929e up to, but not including, c9d8be0e533738b744abb669263c4750d4830009; d98780310719bf4076d975c2ff65c44c7c0d929e up to, but not including, 139a27854bf5ce93ff9805f9f7683b88c13074dc; 6.3 | c9d8be0e533738b744abb669263c4750d4830009, 139a27854bf5ce93ff9805f9f7683b88c13074dc |
| Linux | Linux Kernel | 6.3 up to, but not including, 6.5.5; 6.6 | 6.5.5 |
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: drm/tests: helpers: Avoid a driver uaf when using __drm_kunit_helper_alloc_drm_device() the driver may be dereferenced by device-managed resources up until the device is freed, which is typically later than the kunit-managed resource code frees it. Fix this by simply make the driver device-managed as well. In short, the sequence leading to the UAF is as follows: INIT: Code allocates a struct device as a kunit-managed resource. Code allocates a drm driver as a kunit-managed resource. Code allocates a drm device as a device-managed resource. EXIT: Kunit resource cleanup frees the drm driver Kunit resource cleanup puts the struct device, which starts a device-managed resource cleanup device-managed cleanup calls drm_dev_put() drm_dev_put() dereferences the (now freed) drm driver -> Boom. Related KASAN message: [55272.551542] ================================================================== [55272.551551] BUG: KASAN: slab-use-after-free in drm_dev_put.part.0+0xd4/0xe0 [drm] [55272.551603] Read of size 8 at addr ffff888127502828 by task kunit_try_catch/10353 [55272.551612] CPU: 4 PID: 10353 Comm: kunit_try_catch Tainted: G U N 6.5.0-rc7+ #155 [55272.551620] Hardware name: ASUS System Product Name/PRIME B560M-A AC, BIOS 0403 01/26/2021 [55272.551626] Call Trace: [55272.551629] <TASK> [55272.551633] dump_stack_lvl+0x57/0x90 [55272.551639] print_report+0xcf/0x630 [55272.551645] ? _raw_spin_lock_irqsave+0x5f/0x70 [55272.551652] ? drm_dev_put.part.0+0xd4/0xe0 [drm] [55272.551694] kasan_report+0xd7/0x110 [55272.551699] ? drm_dev_put.part.0+0xd4/0xe0 [drm] [55272.551742] drm_dev_put.part.0+0xd4/0xe0 [drm] [55272.551783] devres_release_all+0x15d/0x1f0 [55272.551790] ? __pfx_devres_release_all+0x10/0x10 [55272.551797] device_unbind_cleanup+0x16/0x1a0 [55272.551802] device_release_driver_internal+0x3e5/0x540 [55272.551808] ? kobject_put+0x5d/0x4b0 [55272.551814] bus_remove_device+0x1f1/0x3f0 [55272.551819] device_del+0x342/0x910 [55272.551826] ? __pfx_device_del+0x10/0x10 [55272.551830] ? lock_release+0x339/0x5e0 [55272.551836] ? kunit_remove_resource+0x128/0x290 [kunit] [55272.551845] ? __pfx_lock_release+0x10/0x10 [55272.551851] platform_device_del.part.0+0x1f/0x1e0 [55272.551856] ? _raw_spin_unlock_irqrestore+0x30/0x60 [55272.551863] kunit_remove_resource+0x195/0x290 [kunit] [55272.551871] ? _raw_spin_unlock_irqrestore+0x30/0x60 [55272.551877] kunit_cleanup+0x78/0x120 [kunit] [55272.551885] ? __kthread_parkme+0xc1/0x1f0 [55272.551891] ? __pfx_kunit_try_run_case_cleanup+0x10/0x10 [kunit] [55272.551900] ? __pfx_kunit_generic_run_threadfn_adapter+0x10/0x10 [kunit] [55272.551909] kunit_generic_run_threadfn_adapter+0x4a/0x90 [kunit] [55272.551919] kthread+0x2e7/0x3c0 [55272.551924] ? __pfx_kthread+0x10/0x10 [55272.551929] ret_from_fork+0x2d/0x70 [55272.551935] ? __pfx_kthread+0x10/0x10 [55272.551940] ret_from_fork_asm+0x1b/0x30 [55272.551948] </TASK> [55272.551953] Allocated by task 10351: [55272.551956] kasan_save_stack+0x1c/0x40 [55272.551962] kasan_set_track+0x21/0x30 [55272.551966] __kasan_kmalloc+0x8b/0x90 [55272.551970] __kmalloc+0x5e/0x160 [55272.551976] kunit_kmalloc_array+0x1c/0x50 [kunit] [55272.551984] drm_exec_test_init+0xfa/0x2c0 [drm_exec_test] [55272.551991] kunit_try_run_case+0xdd/0x250 [kunit] [55272.551999] kunit_generic_run_threadfn_adapter+0x4a/0x90 [kunit] [55272.552008] kthread+0x2e7/0x3c0 [55272.552012] ret_from_fork+0x2d/0x70 [55272.552017] ret_from_fork_asm+0x1b/0x30 [55272.552024] Freed by task 10353: [55272.552027] kasan_save_stack+0x1c/0x40 [55272.552032] kasan_set_track+0x21/0x30 [55272.552036] kasan_save_free_info+0x27/0x40 [55272.552041] __kasan_slab_free+0x106/0x180 [55272.552046] slab_free_freelist_hook+0xb3/0x160 [55272.552051] __kmem_cache_free+0xb2/0x290 [55272.552056] kunit_remove_resource+0x195/0x290 [kunit] [55272.552064] kunit_cleanup+0x7 ---truncated---
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
Recent Use After Free vulnerabilities
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