Linux: Use After Free
CVE-2022-49910 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 dc30e05bb18852303084430c03ca76e69257d9ea, 03af22e23b96fb7ef75fb7885407ef457e8b403d, 6c7407bfbeafc80a04e6eaedcf34d378532a04f2 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 0.27% 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 dc30e05bb18852303084430c03ca76e69257d9ea or 03af22e23b96fb7ef75fb7885407ef457e8b403d or 6c7407bfbeafc80a04e6eaedcf34d378532a04f2 or 4cd094fd5d872862ca278e15b9b51b07e915ef3f, whichever matches your release line, or a later version.
- Update Linux Kernel to 4.9.333 or 4.14.299 or 4.19.265 or 5.4.224, whichever matches your release line, or a later version.
Affected products and versions
| Vendor | Product | Affected versions | Fixed in |
|---|---|---|---|
| Linux | Linux | 4b51dae96731c9d82f5634e75ac7ffd3b9c1b060 up to, but not including, dc30e05bb18852303084430c03ca76e69257d9ea; 4b51dae96731c9d82f5634e75ac7ffd3b9c1b060 up to, but not including, 03af22e23b96fb7ef75fb7885407ef457e8b403d; 4b51dae96731c9d82f5634e75ac7ffd3b9c1b060 up to, but not including, 6c7407bfbeafc80a04e6eaedcf34d378532a04f2; 4b51dae96731c9d82f5634e75ac7ffd3b9c1b060 up to, but not including, 4cd094fd5d872862ca278e15b9b51b07e915ef3f; 4b51dae96731c9d82f5634e75ac7ffd3b9c1b060 up to, but not including, cb1c012099ef5904cd468bdb8d6fcdfdd9bcb569; 4b51dae96731c9d82f5634e75ac7ffd3b9c1b060 up to, but not including, 8278a87bb1eeea94350d675ef961ee5a03341fde; 4b51dae96731c9d82f5634e75ac7ffd3b9c1b060 up to, but not including, 9a04161244603f502c6e453913e51edd59cb70c1; 4b51dae96731c9d82f5634e75ac7ffd3b9c1b060 up to, but not including, 3aff8aaca4e36dc8b17eaa011684881a80238966; and 1 more ranges | dc30e05bb18852303084430c03ca76e69257d9ea, 03af22e23b96fb7ef75fb7885407ef457e8b403d, 6c7407bfbeafc80a04e6eaedcf34d378532a04f2, 4cd094fd5d872862ca278e15b9b51b07e915ef3f, cb1c012099ef5904cd468bdb8d6fcdfdd9bcb569, 8278a87bb1eeea94350d675ef961ee5a03341fde |
| Linux | Linux Kernel | 3.6 up to, but not including, 4.9.333; 4.10 up to, but not including, 4.14.299; 4.15 up to, but not including, 4.19.265; 4.20 up to, but not including, 5.4.224; 5.5 up to, but not including, 5.10.154; 5.11 up to, but not including, 5.15.78; 5.16 up to, but not including, 6.0.8; 6.1 | 4.9.333, 4.14.299, 4.19.265, 5.4.224, 5.10.154, 5.15.78 |
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 | 8.8 | High | CNA |
| CVSS 3.1 | 7.8 | High | NVD |
Official description
In the Linux kernel, the following vulnerability has been resolved: Bluetooth: L2CAP: Fix use-after-free caused by l2cap_reassemble_sdu Fix the race condition between the following two flows that run in parallel: 1. l2cap_reassemble_sdu -> chan->ops->recv (l2cap_sock_recv_cb) -> __sock_queue_rcv_skb. 2. bt_sock_recvmsg -> skb_recv_datagram, skb_free_datagram. An SKB can be queued by the first flow and immediately dequeued and freed by the second flow, therefore the callers of l2cap_reassemble_sdu can't use the SKB after that function returns. However, some places continue accessing struct l2cap_ctrl that resides in the SKB's CB for a short time after l2cap_reassemble_sdu returns, leading to a use-after-free condition (the stack trace is below, line numbers for kernel 5.19.8). Fix it by keeping a local copy of struct l2cap_ctrl. BUG: KASAN: use-after-free in l2cap_rx_state_recv (net/bluetooth/l2cap_core.c:6906) bluetooth Read of size 1 at addr ffff88812025f2f0 by task kworker/u17:3/43169 Workqueue: hci0 hci_rx_work [bluetooth] Call Trace: <TASK> dump_stack_lvl (lib/dump_stack.c:107 (discriminator 4)) print_report.cold (mm/kasan/report.c:314 mm/kasan/report.c:429) ? l2cap_rx_state_recv (net/bluetooth/l2cap_core.c:6906) bluetooth kasan_report (mm/kasan/report.c:162 mm/kasan/report.c:493) ? l2cap_rx_state_recv (net/bluetooth/l2cap_core.c:6906) bluetooth l2cap_rx_state_recv (net/bluetooth/l2cap_core.c:6906) bluetooth l2cap_rx (net/bluetooth/l2cap_core.c:7236 net/bluetooth/l2cap_core.c:7271) bluetooth ret_from_fork (arch/x86/entry/entry_64.S:306) </TASK> Allocated by task 43169: kasan_save_stack (mm/kasan/common.c:39) __kasan_slab_alloc (mm/kasan/common.c:45 mm/kasan/common.c:436 mm/kasan/common.c:469) kmem_cache_alloc_node (mm/slab.h:750 mm/slub.c:3243 mm/slub.c:3293) __alloc_skb (net/core/skbuff.c:414) l2cap_recv_frag (./include/net/bluetooth/bluetooth.h:425 net/bluetooth/l2cap_core.c:8329) bluetooth l2cap_recv_acldata (net/bluetooth/l2cap_core.c:8442) bluetooth hci_rx_work (net/bluetooth/hci_core.c:3642 net/bluetooth/hci_core.c:3832) bluetooth process_one_work (kernel/workqueue.c:2289) worker_thread (./include/linux/list.h:292 kernel/workqueue.c:2437) kthread (kernel/kthread.c:376) ret_from_fork (arch/x86/entry/entry_64.S:306) Freed by task 27920: kasan_save_stack (mm/kasan/common.c:39) kasan_set_track (mm/kasan/common.c:45) kasan_set_free_info (mm/kasan/generic.c:372) ____kasan_slab_free (mm/kasan/common.c:368 mm/kasan/common.c:328) slab_free_freelist_hook (mm/slub.c:1780) kmem_cache_free (mm/slub.c:3536 mm/slub.c:3553) skb_free_datagram (./include/net/sock.h:1578 ./include/net/sock.h:1639 net/core/datagram.c:323) bt_sock_recvmsg (net/bluetooth/af_bluetooth.c:295) bluetooth l2cap_sock_recvmsg (net/bluetooth/l2cap_sock.c:1212) bluetooth sock_read_iter (net/socket.c:1087) new_sync_read (./include/linux/fs.h:2052 fs/read_write.c:401) vfs_read (fs/read_write.c:482) ksys_read (fs/read_write.c:620) do_syscall_64 (arch/x86/entry/common.c:50 arch/x86/entry/common.c:80) entry_SYSCALL_64_after_hwframe (arch/x86/entry/entry_64.S:120)
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.
- Record last changed materially (score, affected products, status or references).
References
Patches and release notes
- git.kernel.org/stable/c/03af22e23b96fb7ef75fb7885407ef457e8b403d
- git.kernel.org/stable/c/3aff8aaca4e36dc8b17eaa011684881a80238966
- git.kernel.org/stable/c/4cd094fd5d872862ca278e15b9b51b07e915ef3f
- git.kernel.org/stable/c/6c7407bfbeafc80a04e6eaedcf34d378532a04f2
- git.kernel.org/stable/c/8278a87bb1eeea94350d675ef961ee5a03341fde
- git.kernel.org/stable/c/9a04161244603f502c6e453913e51edd59cb70c1
- git.kernel.org/stable/c/cb1c012099ef5904cd468bdb8d6fcdfdd9bcb569
- git.kernel.org/stable/c/dc30e05bb18852303084430c03ca76e69257d9ea
Recent Use After Free vulnerabilities
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