Linux: Use After Free
CVE-2023-52885 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 c7b8c2d06e437639694abe76978e915cfb73f428, dfc896c4a75cb8cd7cb2dfd9b469cf1e3f004254, 42725e5c1b181b757ba11d804443922982334d9b 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 0.56% 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 c7b8c2d06e437639694abe76978e915cfb73f428 or dfc896c4a75cb8cd7cb2dfd9b469cf1e3f004254 or 42725e5c1b181b757ba11d804443922982334d9b or cd5ec3ee52ce4b7e283cc11facfa420c297c8065, whichever matches your release line, or a later version.
- Update Linux Kernel to 4.14.322 or 4.19.291 or 5.4.251 or 5.10.188, whichever matches your release line, or a later version.
Affected products and versions
| Vendor | Product | Affected versions | Fixed in |
|---|---|---|---|
| Linux | Linux | fa9251afc33c81606d70cfe91800a779096442ec up to, but not including, c7b8c2d06e437639694abe76978e915cfb73f428; fa9251afc33c81606d70cfe91800a779096442ec up to, but not including, dfc896c4a75cb8cd7cb2dfd9b469cf1e3f004254; fa9251afc33c81606d70cfe91800a779096442ec up to, but not including, 42725e5c1b181b757ba11d804443922982334d9b; fa9251afc33c81606d70cfe91800a779096442ec up to, but not including, cd5ec3ee52ce4b7e283cc11facfa420c297c8065; fa9251afc33c81606d70cfe91800a779096442ec up to, but not including, fbf4ace39b2e4f3833236afbb2336edbafd75eee; fa9251afc33c81606d70cfe91800a779096442ec up to, but not including, ef047411887ff0845afd642d6a687819308e1a4e; fa9251afc33c81606d70cfe91800a779096442ec up to, but not including, 7e1f989055622fd086c5dfb291fc72adf5660b6f; fa9251afc33c81606d70cfe91800a779096442ec up to, but not including, fc80fc2d4e39137869da3150ee169b40bf879287; and 1 more ranges | c7b8c2d06e437639694abe76978e915cfb73f428, dfc896c4a75cb8cd7cb2dfd9b469cf1e3f004254, 42725e5c1b181b757ba11d804443922982334d9b, cd5ec3ee52ce4b7e283cc11facfa420c297c8065, fbf4ace39b2e4f3833236afbb2336edbafd75eee, ef047411887ff0845afd642d6a687819308e1a4e |
| Linux | Linux Kernel | 4.8 up to, but not including, 4.14.322; 4.15 up to, but not including, 4.19.291; 4.20 up to, but not including, 5.4.251; 5.5 up to, but not including, 5.10.188; 5.11 up to, but not including, 5.15.121; 5.16 up to, but not including, 6.1.39; 6.2 up to, but not including, 6.4.4 | 4.14.322, 4.19.291, 5.4.251, 5.10.188, 5.15.121, 6.1.39 |
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 | 8.1 | High | CNA |
| CVSS 3.1 | 7.8 | High | NVD |
Official description
In the Linux kernel, the following vulnerability has been resolved: SUNRPC: Fix UAF in svc_tcp_listen_data_ready() After the listener svc_sock is freed, and before invoking svc_tcp_accept() for the established child sock, there is a window that the newsock retaining a freed listener svc_sock in sk_user_data which cloning from parent. In the race window, if data is received on the newsock, we will observe use-after-free report in svc_tcp_listen_data_ready(). Reproduce by two tasks: 1. while :; do rpc.nfsd 0 ; rpc.nfsd; done 2. while :; do echo "" | ncat -4 127.0.0.1 2049 ; done KASAN report: ================================================================== BUG: KASAN: slab-use-after-free in svc_tcp_listen_data_ready+0x1cf/0x1f0 [sunrpc] Read of size 8 at addr ffff888139d96228 by task nc/102553 CPU: 7 PID: 102553 Comm: nc Not tainted 6.3.0+ #18 Hardware name: VMware, Inc. VMware Virtual Platform/440BX Desktop Reference Platform, BIOS 6.00 11/12/2020 Call Trace: <IRQ> dump_stack_lvl+0x33/0x50 print_address_description.constprop.0+0x27/0x310 print_report+0x3e/0x70 kasan_report+0xae/0xe0 svc_tcp_listen_data_ready+0x1cf/0x1f0 [sunrpc] tcp_data_queue+0x9f4/0x20e0 tcp_rcv_established+0x666/0x1f60 tcp_v4_do_rcv+0x51c/0x850 tcp_v4_rcv+0x23fc/0x2e80 ip_protocol_deliver_rcu+0x62/0x300 ip_local_deliver_finish+0x267/0x350 ip_local_deliver+0x18b/0x2d0 ip_rcv+0x2fb/0x370 __netif_receive_skb_one_core+0x166/0x1b0 process_backlog+0x24c/0x5e0 __napi_poll+0xa2/0x500 net_rx_action+0x854/0xc90 __do_softirq+0x1bb/0x5de do_softirq+0xcb/0x100 </IRQ> <TASK> ... </TASK> Allocated by task 102371: kasan_save_stack+0x1e/0x40 kasan_set_track+0x21/0x30 __kasan_kmalloc+0x7b/0x90 svc_setup_socket+0x52/0x4f0 [sunrpc] svc_addsock+0x20d/0x400 [sunrpc] __write_ports_addfd+0x209/0x390 [nfsd] write_ports+0x239/0x2c0 [nfsd] nfsctl_transaction_write+0xac/0x110 [nfsd] vfs_write+0x1c3/0xae0 ksys_write+0xed/0x1c0 do_syscall_64+0x38/0x90 entry_SYSCALL_64_after_hwframe+0x72/0xdc Freed by task 102551: kasan_save_stack+0x1e/0x40 kasan_set_track+0x21/0x30 kasan_save_free_info+0x2a/0x50 __kasan_slab_free+0x106/0x190 __kmem_cache_free+0x133/0x270 svc_xprt_free+0x1e2/0x350 [sunrpc] svc_xprt_destroy_all+0x25a/0x440 [sunrpc] nfsd_put+0x125/0x240 [nfsd] nfsd_svc+0x2cb/0x3c0 [nfsd] write_threads+0x1ac/0x2a0 [nfsd] nfsctl_transaction_write+0xac/0x110 [nfsd] vfs_write+0x1c3/0xae0 ksys_write+0xed/0x1c0 do_syscall_64+0x38/0x90 entry_SYSCALL_64_after_hwframe+0x72/0xdc Fix the UAF by simply doing nothing in svc_tcp_listen_data_ready() if state != TCP_LISTEN, that will avoid dereferencing svsk for all child socket.
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/42725e5c1b181b757ba11d804443922982334d9b
- git.kernel.org/stable/c/7e1f989055622fd086c5dfb291fc72adf5660b6f
- git.kernel.org/stable/c/c7b8c2d06e437639694abe76978e915cfb73f428
- git.kernel.org/stable/c/cd5ec3ee52ce4b7e283cc11facfa420c297c8065
- git.kernel.org/stable/c/dfc896c4a75cb8cd7cb2dfd9b469cf1e3f004254
- git.kernel.org/stable/c/ef047411887ff0845afd642d6a687819308e1a4e
- git.kernel.org/stable/c/fbf4ace39b2e4f3833236afbb2336edbafd75eee
- git.kernel.org/stable/c/fc80fc2d4e39137869da3150ee169b40bf879287
Recent Use After Free vulnerabilities
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