Linux: Use After Free
CVE-2023-52438 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 a53e15e592b4dcc91c3a3b8514e484a0bdbc53a3, c8c1158ffb007197f31f9d9170cf13e4f34cbb5c, 8ad4d580e8aff8de2a4d57c5930fcc29f1ffd4a6 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 0.29% 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 a53e15e592b4dcc91c3a3b8514e484a0bdbc53a3 or c8c1158ffb007197f31f9d9170cf13e4f34cbb5c or 8ad4d580e8aff8de2a4d57c5930fcc29f1ffd4a6 or 9fa04c93f24138747807fe75b5591bb680098f56, whichever matches your release line, or a later version.
- Update Linux Kernel to 5.4.268 or 5.10.209 or 5.15.148 or 6.1.74, whichever matches your release line, or a later version.
Affected products and versions
| Vendor | Product | Affected versions | Fixed in |
|---|---|---|---|
| Linux | Linux | dd2283f2605e3b3e9c61bcae844b34f2afa4813f up to, but not including, a53e15e592b4dcc91c3a3b8514e484a0bdbc53a3; dd2283f2605e3b3e9c61bcae844b34f2afa4813f up to, but not including, c8c1158ffb007197f31f9d9170cf13e4f34cbb5c; dd2283f2605e3b3e9c61bcae844b34f2afa4813f up to, but not including, 8ad4d580e8aff8de2a4d57c5930fcc29f1ffd4a6; dd2283f2605e3b3e9c61bcae844b34f2afa4813f up to, but not including, 9fa04c93f24138747807fe75b5591bb680098f56; dd2283f2605e3b3e9c61bcae844b34f2afa4813f up to, but not including, a49087ab93508b60d9b8add91707a22dda832869; dd2283f2605e3b3e9c61bcae844b34f2afa4813f up to, but not including, e074686e993ff1be5f21b085a3b1b4275ccd5727; dd2283f2605e3b3e9c61bcae844b34f2afa4813f up to, but not including, 3f489c2067c5824528212b0fc18b28d51332d906; 4.20 | a53e15e592b4dcc91c3a3b8514e484a0bdbc53a3, c8c1158ffb007197f31f9d9170cf13e4f34cbb5c, 8ad4d580e8aff8de2a4d57c5930fcc29f1ffd4a6, 9fa04c93f24138747807fe75b5591bb680098f56, a49087ab93508b60d9b8add91707a22dda832869, e074686e993ff1be5f21b085a3b1b4275ccd5727 |
| Linux | Linux Kernel | 4.20.0 up to, but not including, 5.4.268; 5.5.0 up to, but not including, 5.10.209; 5.11.0 up to, but not including, 5.15.148; 5.16.0 up to, but not including, 6.1.74; 6.2.0 up to, but not including, 6.6.13; 6.7.0 up to, but not including, 6.7.1 | 5.4.268, 5.10.209, 5.15.148, 6.1.74, 6.6.13, 6.7.1 |
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: binder: fix use-after-free in shinker's callback The mmap read lock is used during the shrinker's callback, which means that using alloc->vma pointer isn't safe as it can race with munmap(). As of commit dd2283f2605e ("mm: mmap: zap pages with read mmap_sem in munmap") the mmap lock is downgraded after the vma has been isolated. I was able to reproduce this issue by manually adding some delays and triggering page reclaiming through the shrinker's debug sysfs. The following KASAN report confirms the UAF: ================================================================== BUG: KASAN: slab-use-after-free in zap_page_range_single+0x470/0x4b8 Read of size 8 at addr ffff356ed50e50f0 by task bash/478 CPU: 1 PID: 478 Comm: bash Not tainted 6.6.0-rc5-00055-g1c8b86a3799f-dirty #70 Hardware name: linux,dummy-virt (DT) Call trace: zap_page_range_single+0x470/0x4b8 binder_alloc_free_page+0x608/0xadc __list_lru_walk_one+0x130/0x3b0 list_lru_walk_node+0xc4/0x22c binder_shrink_scan+0x108/0x1dc shrinker_debugfs_scan_write+0x2b4/0x500 full_proxy_write+0xd4/0x140 vfs_write+0x1ac/0x758 ksys_write+0xf0/0x1dc __arm64_sys_write+0x6c/0x9c Allocated by task 492: kmem_cache_alloc+0x130/0x368 vm_area_alloc+0x2c/0x190 mmap_region+0x258/0x18bc do_mmap+0x694/0xa60 vm_mmap_pgoff+0x170/0x29c ksys_mmap_pgoff+0x290/0x3a0 __arm64_sys_mmap+0xcc/0x144 Freed by task 491: kmem_cache_free+0x17c/0x3c8 vm_area_free_rcu_cb+0x74/0x98 rcu_core+0xa38/0x26d4 rcu_core_si+0x10/0x1c __do_softirq+0x2fc/0xd24 Last potentially related work creation: __call_rcu_common.constprop.0+0x6c/0xba0 call_rcu+0x10/0x1c vm_area_free+0x18/0x24 remove_vma+0xe4/0x118 do_vmi_align_munmap.isra.0+0x718/0xb5c do_vmi_munmap+0xdc/0x1fc __vm_munmap+0x10c/0x278 __arm64_sys_munmap+0x58/0x7c Fix this issue by performing instead a vma_lookup() which will fail to find the vma that was isolated before the mmap lock downgrade. Note that this option has better performance than upgrading to a mmap write lock which would increase contention. Plus, mmap_write_trylock() has been recently removed anyway.
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
- git.kernel.org/stable/c/3f489c2067c5824528212b0fc18b28d51332d906
- git.kernel.org/stable/c/8ad4d580e8aff8de2a4d57c5930fcc29f1ffd4a6
- git.kernel.org/stable/c/9fa04c93f24138747807fe75b5591bb680098f56
- git.kernel.org/stable/c/a49087ab93508b60d9b8add91707a22dda832869
- git.kernel.org/stable/c/a53e15e592b4dcc91c3a3b8514e484a0bdbc53a3
- git.kernel.org/stable/c/c8c1158ffb007197f31f9d9170cf13e4f34cbb5c
- git.kernel.org/stable/c/e074686e993ff1be5f21b085a3b1b4275ccd5727
Other references
Recent Use After Free vulnerabilities
- 9.8 Critical severity
- 8.1 High severity
- 9.1 Critical severity
- 9.8 Critical severity
- 9.8 Critical severity
- 7.8 High severity
Spotted an error? Tell us.