CVE-2023-53246

cifs: fix DFS traversal oops without CONFIG_CIFS_DFS_UPCALL

Severity Score

5.5

*CVSS v3.1

Exploit Likelihood

*EPSS

Affected Versions

*CPE

Public Exploits

*Multiple Sources

Exploited in Wild

*KEV

Decision

*SSVC

Descriptions

In the Linux kernel, the following vulnerability has been resolved: cifs: fix DFS traversal oops without CONFIG_CIFS_DFS_UPCALL When compiled with CONFIG_CIFS_DFS_UPCALL disabled, cifs_dfs_d_automount
is NULL. cifs.ko logic for mapping CIFS_FATTR_DFS_REFERRAL attributes to
S_AUTOMOUNT and corresponding dentry flags is retained regardless of
CONFIG_CIFS_DFS_UPCALL, leading to a NULL pointer dereference in
VFS follow_automount() when traversing a DFS referral link: BUG: kernel NULL pointer dereference, address: 0000000000000000 ... Call Trace: <TASK> __traverse_mounts+0xb5/0x220 ? cifs_revalidate_mapping+0x65/0xc0 [cifs] step_into+0x195/0x610 ? lookup_fast+0xe2/0xf0 path_lookupat+0x64/0x140 filename_lookup+0xc2/0x140 ? __create_object+0x299/0x380 ? kmem_cache_alloc+0x119/0x220 ? user_path_at_empty+0x31/0x50 user_path_at_empty+0x31/0x50 __x64_sys_chdir+0x2a/0xd0 ? exit_to_user_mode_prepare+0xca/0x100 do_syscall_64+0x42/0x90 entry_SYSCALL_64_after_hwframe+0x72/0xdc This fix adds an inline cifs_dfs_d_automount() {return -EREMOTE} handler
when CONFIG_CIFS_DFS_UPCALL is disabled. An alternative would be to
avoid flagging S_AUTOMOUNT, etc. without CONFIG_CIFS_DFS_UPCALL. This
approach was chosen as it provides more control over the error path.

In the Linux kernel, the following vulnerability has been resolved: cifs: fix DFS traversal oops without CONFIG_CIFS_DFS_UPCALL When compiled with CONFIG_CIFS_DFS_UPCALL disabled, cifs_dfs_d_automount is NULL. cifs.ko logic for mapping CIFS_FATTR_DFS_REFERRAL attributes to S_AUTOMOUNT and corresponding dentry flags is retained regardless of CONFIG_CIFS_DFS_UPCALL, leading to a NULL pointer dereference in VFS follow_automount() when traversing a DFS referral link: BUG: kernel NULL pointer dereference, address: 0000000000000000 ... Call Trace: <TASK> __traverse_mounts+0xb5/0x220 ? cifs_revalidate_mapping+0x65/0xc0 [cifs] step_into+0x195/0x610 ? lookup_fast+0xe2/0xf0 path_lookupat+0x64/0x140 filename_lookup+0xc2/0x140 ? __create_object+0x299/0x380 ? kmem_cache_alloc+0x119/0x220 ? user_path_at_empty+0x31/0x50 user_path_at_empty+0x31/0x50 __x64_sys_chdir+0x2a/0xd0 ? exit_to_user_mode_prepare+0xca/0x100 do_syscall_64+0x42/0x90 entry_SYSCALL_64_after_hwframe+0x72/0xdc This fix adds an inline cifs_dfs_d_automount() {return -EREMOTE} handler when CONFIG_CIFS_DFS_UPCALL is disabled. An alternative would be to avoid flagging S_AUTOMOUNT, etc. without CONFIG_CIFS_DFS_UPCALL. This approach was chosen as it provides more control over the error path.

This update provides the initial livepatch for this kernel update. This update does not contain any fixes and will be updated with livepatches later.

*Credits: N/A

Attack Vector

Local

Attack Complexity

Low

Privileges Required

Low

User Interaction

None

Scope

Unchanged

Confidentiality

None

Integrity

None

Availability

High

Attack Vector

Local

Attack Complexity

Low

Authentication

Single

Confidentiality

None

Integrity

None

Availability

Complete

* Common Vulnerability Scoring System

SSVC

Decision:-

Exploitation

Automatable

Tech. Impact

* Organization's Worst-case Scenario

Timeline

2025-09-15 CVE Reserved
2025-09-15 CVE Published
2026-01-05 CVE Updated
2026-01-05 EPSS Updated
---------- Exploited in Wild
---------- KEV Due Date
---------- First Exploit

CWE

CAPEC

References (9)

URL	Tag	Source
https://git.kernel.org/stable/c/25e195aa1e607f129ab912d29fcfc79239703307	Vuln. Introduced
https://git.kernel.org/stable/c/657d7c215ca974d366ab1808213f716e1e3aa950
https://git.kernel.org/stable/c/8afb1fabcec1929db46977e84baeee0cc0e79242
https://git.kernel.org/stable/c/8cd7dbc9c46d51e00a0a8372e07cc1cbb8d24a77

URL	Date	SRC

URL	Date	SRC
https://git.kernel.org/stable/c/26a32a212bc540f4773cd6af8cf73e967d72569c	2023-04-05
https://git.kernel.org/stable/c/b64305185b76f1d5145ce594ff48f3f0e70695bd	2023-04-05
https://git.kernel.org/stable/c/b7d854c33ab48e55fc233699bbefe39ec9bb5c05	2023-04-06
https://git.kernel.org/stable/c/1e144b68208e98fd4602c842a7149ba5f41d87fb	2023-04-06
https://git.kernel.org/stable/c/179a88a8558bbf42991d361595281f3e45d7edfc	2023-03-30

URL	Date	SRC

Affected Vendors, Products, and Versions

Vendor		Product				Version		Other		Status
Vendor	Product	Version	Other	Status	<-- -->	Vendor	Product	Version	Other	Status
Linux Search vendor "Linux"		Linux Kernel Search vendor "Linux" for product "Linux Kernel"				>= 5.7 < 5.10.177 Search vendor "Linux" for product "Linux Kernel" and version " >= 5.7 < 5.10.177"		en		Affected
Linux Search vendor "Linux"		Linux Kernel Search vendor "Linux" for product "Linux Kernel"				>= 5.7 < 5.15.106 Search vendor "Linux" for product "Linux Kernel" and version " >= 5.7 < 5.15.106"		en		Affected
Linux Search vendor "Linux"		Linux Kernel Search vendor "Linux" for product "Linux Kernel"				>= 5.7 < 6.1.23 Search vendor "Linux" for product "Linux Kernel" and version " >= 5.7 < 6.1.23"		en		Affected
Linux Search vendor "Linux"		Linux Kernel Search vendor "Linux" for product "Linux Kernel"				>= 5.7 < 6.2.10 Search vendor "Linux" for product "Linux Kernel" and version " >= 5.7 < 6.2.10"		en		Affected
Linux Search vendor "Linux"		Linux Kernel Search vendor "Linux" for product "Linux Kernel"				>= 5.7 < 6.3 Search vendor "Linux" for product "Linux Kernel" and version " >= 5.7 < 6.3"		en		Affected