Linux: Use After Free
CVE-2022-48726 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 75c610212b9f1756b9384911d3a2c347eee8031c, 2923948ffe0835f7114e948b35bcc42bc9b3baa1, ee2477e8ccd3d978eeac0dc5a981b286d9bb7b0a 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 0.24% 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 75c610212b9f1756b9384911d3a2c347eee8031c or 2923948ffe0835f7114e948b35bcc42bc9b3baa1 or ee2477e8ccd3d978eeac0dc5a981b286d9bb7b0a or 36e8169ec973359f671f9ec7213547059cae972e, whichever matches your release line, or a later version.
- Update Linux Kernel to 5.10.99 or 5.15.22 or 5.16.8, whichever matches your release line, or a later version.
Affected products and versions
| Vendor | Product | Affected versions | Fixed in |
|---|---|---|---|
| Linux | Linux | 95fe51096b7adf1d1e7315c49c75e2f75f162584 up to, but not including, 75c610212b9f1756b9384911d3a2c347eee8031c; 95fe51096b7adf1d1e7315c49c75e2f75f162584 up to, but not including, 2923948ffe0835f7114e948b35bcc42bc9b3baa1; 95fe51096b7adf1d1e7315c49c75e2f75f162584 up to, but not including, ee2477e8ccd3d978eeac0dc5a981b286d9bb7b0a; 95fe51096b7adf1d1e7315c49c75e2f75f162584 up to, but not including, 36e8169ec973359f671f9ec7213547059cae972e; 5.10 | 75c610212b9f1756b9384911d3a2c347eee8031c, 2923948ffe0835f7114e948b35bcc42bc9b3baa1, ee2477e8ccd3d978eeac0dc5a981b286d9bb7b0a, 36e8169ec973359f671f9ec7213547059cae972e |
| Linux | Linux Kernel | 5.10 up to, but not including, 5.10.99; 5.11 up to, but not including, 5.15.22; 5.16 up to, but not including, 5.16.8; 5.17 | 5.10.99, 5.15.22, 5.16.8 |
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: RDMA/ucma: Protect mc during concurrent multicast leaves Partially revert the commit mentioned in the Fixes line to make sure that allocation and erasing multicast struct are locked. BUG: KASAN: use-after-free in ucma_cleanup_multicast drivers/infiniband/core/ucma.c:491 [inline] BUG: KASAN: use-after-free in ucma_destroy_private_ctx+0x914/0xb70 drivers/infiniband/core/ucma.c:579 Read of size 8 at addr ffff88801bb74b00 by task syz-executor.1/25529 CPU: 0 PID: 25529 Comm: syz-executor.1 Not tainted 5.16.0-rc7-syzkaller #0 Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011 Call Trace: __dump_stack lib/dump_stack.c:88 [inline] dump_stack_lvl+0xcd/0x134 lib/dump_stack.c:106 print_address_description.constprop.0.cold+0x8d/0x320 mm/kasan/report.c:247 __kasan_report mm/kasan/report.c:433 [inline] kasan_report.cold+0x83/0xdf mm/kasan/report.c:450 ucma_cleanup_multicast drivers/infiniband/core/ucma.c:491 [inline] ucma_destroy_private_ctx+0x914/0xb70 drivers/infiniband/core/ucma.c:579 ucma_destroy_id+0x1e6/0x280 drivers/infiniband/core/ucma.c:614 ucma_write+0x25c/0x350 drivers/infiniband/core/ucma.c:1732 vfs_write+0x28e/0xae0 fs/read_write.c:588 ksys_write+0x1ee/0x250 fs/read_write.c:643 do_syscall_x64 arch/x86/entry/common.c:50 [inline] do_syscall_64+0x35/0xb0 arch/x86/entry/common.c:80 entry_SYSCALL_64_after_hwframe+0x44/0xae Currently the xarray search can touch a concurrently freeing mc as the xa_for_each() is not surrounded by any lock. Rather than hold the lock for a full scan hold it only for the effected items, which is usually an empty list.
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
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