Linux: Use After Free
CVE-2022-48674 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 8ddd001cef5e82d19192e6861068463ecca5f556, 94c34faaafe7b55adc2d8d881db195b646959b9e, 2f44013e39984c127c6efedf70e6b5f4e9dcf315 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 0.23% 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 8ddd001cef5e82d19192e6861068463ecca5f556 or 94c34faaafe7b55adc2d8d881db195b646959b9e or 2f44013e39984c127c6efedf70e6b5f4e9dcf315 or 4.20, whichever matches your release line, or a later version.
- Update Linux Kernel to 4.20 or 5.15.68 or 5.19.9, whichever matches your release line, or a later version.
Affected products and versions
| Vendor | Product | Affected versions | Fixed in |
|---|---|---|---|
| Linux | Linux | 73f5c66df3e26ab750cefcb9a3e08c71c9f79cad up to, but not including, 8ddd001cef5e82d19192e6861068463ecca5f556; 73f5c66df3e26ab750cefcb9a3e08c71c9f79cad up to, but not including, 94c34faaafe7b55adc2d8d881db195b646959b9e; 73f5c66df3e26ab750cefcb9a3e08c71c9f79cad up to, but not including, 2f44013e39984c127c6efedf70e6b5f4e9dcf315; 08ec9e6892cc792d7f8fe4d13bd8a0e91fb23488; 78c46113413bea1cc345757112aa2642e0f66de5; 4.19.26 up to, but not including, 4.20; 4.20.13 up to, but not including, 4.21; 5.0 | 8ddd001cef5e82d19192e6861068463ecca5f556, 94c34faaafe7b55adc2d8d881db195b646959b9e, 2f44013e39984c127c6efedf70e6b5f4e9dcf315, 4.20, 4.21 |
| Linux | Linux Kernel | 4.19.26 up to, but not including, 4.20; 4.20.13 up to, but not including, 5.15.68; 5.16 up to, but not including, 5.19.9; 6.0 | 4.20, 5.15.68, 5.19.9 |
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 |
| CVSS 3.1 | 6.2 | Medium | CISA (ADP) |
Official description
In the Linux kernel, the following vulnerability has been resolved: erofs: fix pcluster use-after-free on UP platforms During stress testing with CONFIG_SMP disabled, KASAN reports as below: ================================================================== BUG: KASAN: use-after-free in __mutex_lock+0xe5/0xc30 Read of size 8 at addr ffff8881094223f8 by task stress/7789 CPU: 0 PID: 7789 Comm: stress Not tainted 6.0.0-rc1-00002-g0d53d2e882f9 #3 Hardware name: Red Hat KVM, BIOS 0.5.1 01/01/2011 Call Trace: <TASK> .. __mutex_lock+0xe5/0xc30 .. z_erofs_do_read_page+0x8ce/0x1560 .. z_erofs_readahead+0x31c/0x580 .. Freed by task 7787 kasan_save_stack+0x1e/0x40 kasan_set_track+0x20/0x30 kasan_set_free_info+0x20/0x40 __kasan_slab_free+0x10c/0x190 kmem_cache_free+0xed/0x380 rcu_core+0x3d5/0xc90 __do_softirq+0x12d/0x389 Last potentially related work creation: kasan_save_stack+0x1e/0x40 __kasan_record_aux_stack+0x97/0xb0 call_rcu+0x3d/0x3f0 erofs_shrink_workstation+0x11f/0x210 erofs_shrink_scan+0xdc/0x170 shrink_slab.constprop.0+0x296/0x530 drop_slab+0x1c/0x70 drop_caches_sysctl_handler+0x70/0x80 proc_sys_call_handler+0x20a/0x2f0 vfs_write+0x555/0x6c0 ksys_write+0xbe/0x160 do_syscall_64+0x3b/0x90 The root cause is that erofs_workgroup_unfreeze() doesn't reset to orig_val thus it causes a race that the pcluster reuses unexpectedly before freeing. Since UP platforms are quite rare now, such path becomes unnecessary. Let's drop such specific-designed path directly instead.
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
- 9.8 Critical severity
- 7.8 High severity
- 7.8 High severity
- 7.4 High severity
- 9.8 Critical severity
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