Linux: Use After Free
CVE-2023-52572 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 fe87e2d0e6265859c659a3ef1e2559a83c5e8e68, 99960d282fba6634fa758df4124cb73ef8a77d8a, ed3b36f351d97dacb62cd0f399e8cf79f73bd30a 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 fe87e2d0e6265859c659a3ef1e2559a83c5e8e68 or 99960d282fba6634fa758df4124cb73ef8a77d8a or ed3b36f351d97dacb62cd0f399e8cf79f73bd30a or 908b3b5e97d25e879de3d1f172a255665491c2c3, whichever matches your release line, or a later version.
- Update Linux Kernel to 5.4.297 or 5.10.237 or 5.15.181 or 6.1.56, whichever matches your release line, or a later version.
Affected products and versions
| Vendor | Product | Affected versions | Fixed in |
|---|---|---|---|
| Linux | Linux | ec637e3ffb6b978143652477c7c5f96c9519b691 up to, but not including, fe87e2d0e6265859c659a3ef1e2559a83c5e8e68; ec637e3ffb6b978143652477c7c5f96c9519b691 up to, but not including, 99960d282fba6634fa758df4124cb73ef8a77d8a; ec637e3ffb6b978143652477c7c5f96c9519b691 up to, but not including, ed3b36f351d97dacb62cd0f399e8cf79f73bd30a; ec637e3ffb6b978143652477c7c5f96c9519b691 up to, but not including, 908b3b5e97d25e879de3d1f172a255665491c2c3; ec637e3ffb6b978143652477c7c5f96c9519b691 up to, but not including, 76569e3819e0bb59fc19b1b8688b017e627c268a; ec637e3ffb6b978143652477c7c5f96c9519b691 up to, but not including, d527f51331cace562393a8038d870b3e9916686f; 2.6.16 | fe87e2d0e6265859c659a3ef1e2559a83c5e8e68, 99960d282fba6634fa758df4124cb73ef8a77d8a, ed3b36f351d97dacb62cd0f399e8cf79f73bd30a, 908b3b5e97d25e879de3d1f172a255665491c2c3, 76569e3819e0bb59fc19b1b8688b017e627c268a, d527f51331cace562393a8038d870b3e9916686f |
| Debian | Debian Linux | 11.0 | Not stated |
| Linux | Linux Kernel | 2.6.16 up to, but not including, 5.4.297; 5.5 up to, but not including, 5.10.237; 5.11 up to, but not including, 5.15.181; 5.16 up to, but not including, 6.1.56; 6.2 up to, but not including, 6.5.6; 6.6 | 5.4.297, 5.10.237, 5.15.181, 6.1.56, 6.5.6 |
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: cifs: Fix UAF in cifs_demultiplex_thread() There is a UAF when xfstests on cifs: BUG: KASAN: use-after-free in smb2_is_network_name_deleted+0x27/0x160 Read of size 4 at addr ffff88810103fc08 by task cifsd/923 CPU: 1 PID: 923 Comm: cifsd Not tainted 6.1.0-rc4+ #45 ... Call Trace: <TASK> dump_stack_lvl+0x34/0x44 print_report+0x171/0x472 kasan_report+0xad/0x130 kasan_check_range+0x145/0x1a0 smb2_is_network_name_deleted+0x27/0x160 cifs_demultiplex_thread.cold+0x172/0x5a4 kthread+0x165/0x1a0 ret_from_fork+0x1f/0x30 </TASK> Allocated by task 923: kasan_save_stack+0x1e/0x40 kasan_set_track+0x21/0x30 __kasan_slab_alloc+0x54/0x60 kmem_cache_alloc+0x147/0x320 mempool_alloc+0xe1/0x260 cifs_small_buf_get+0x24/0x60 allocate_buffers+0xa1/0x1c0 cifs_demultiplex_thread+0x199/0x10d0 kthread+0x165/0x1a0 ret_from_fork+0x1f/0x30 Freed by task 921: kasan_save_stack+0x1e/0x40 kasan_set_track+0x21/0x30 kasan_save_free_info+0x2a/0x40 ____kasan_slab_free+0x143/0x1b0 kmem_cache_free+0xe3/0x4d0 cifs_small_buf_release+0x29/0x90 SMB2_negotiate+0x8b7/0x1c60 smb2_negotiate+0x51/0x70 cifs_negotiate_protocol+0xf0/0x160 cifs_get_smb_ses+0x5fa/0x13c0 mount_get_conns+0x7a/0x750 cifs_mount+0x103/0xd00 cifs_smb3_do_mount+0x1dd/0xcb0 smb3_get_tree+0x1d5/0x300 vfs_get_tree+0x41/0xf0 path_mount+0x9b3/0xdd0 __x64_sys_mount+0x190/0x1d0 do_syscall_64+0x35/0x80 entry_SYSCALL_64_after_hwframe+0x46/0xb0 The UAF is because: mount(pid: 921) | cifsd(pid: 923) -------------------------------|------------------------------- | cifs_demultiplex_thread SMB2_negotiate | cifs_send_recv | compound_send_recv | smb_send_rqst | wait_for_response | wait_event_state [1] | | standard_receive3 | cifs_handle_standard | handle_mid | mid->resp_buf = buf; [2] | dequeue_mid [3] KILL the process [4] | resp_iov[i].iov_base = buf | free_rsp_buf [5] | | is_network_name_deleted [6] | callback 1. After send request to server, wait the response until mid->mid_state != SUBMITTED; 2. Receive response from server, and set it to mid; 3. Set the mid state to RECEIVED; 4. Kill the process, the mid state already RECEIVED, get 0; 5. Handle and release the negotiate response; 6. UAF. It can be easily reproduce with add some delay in [3] - [6]. Only sync call has the problem since async call's callback is executed in cifsd process. Add an extra state to mark the mid state to READY before wakeup the waitter, then it can get the resp safely.
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/76569e3819e0bb59fc19b1b8688b017e627c268a
- git.kernel.org/stable/c/908b3b5e97d25e879de3d1f172a255665491c2c3
- git.kernel.org/stable/c/99960d282fba6634fa758df4124cb73ef8a77d8a
- git.kernel.org/stable/c/d527f51331cace562393a8038d870b3e9916686f
- git.kernel.org/stable/c/ed3b36f351d97dacb62cd0f399e8cf79f73bd30a
- git.kernel.org/stable/c/fe87e2d0e6265859c659a3ef1e2559a83c5e8e68
Third-party and government advisories
- lists.debian.org/debian-lts-announce/2025/05/msg00030.htmlMailing List, Third Party Advisory
Recent Use After Free vulnerabilities
- 7.8 High severity
- 7.8 High severity
- 7.8 High severity
- 7.8 High severity
- 7.0 High severity
- 7.8 High severity
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