CVE-2025-21725
NoneCVSS
—
EPSS
0.4%
Published
Feb 27, 2025
CISA due date
—
Cloudanix analysis
A missing network speed value in some file-sharing connections can make the computer crash when checking connection details.
- Exploitation
- Local Privilege
- Attacker needs
- Local User
- Complexity
- Low
- Impact
- Denial Of Service
- Component
- OS kernel
- Class
- Improper Input Validation
- Remediation
- Patch
- Effort
- Medium
- Patch risk
- Low
What it actually does
Unset NETWORK_INTERFACE_INFO::LinkSpeed value triggers a divide-by-zero in cifs_debug_data_proc_show leading to kernel oops.
Why it matters to the business
Systems using SMB client connections may experience unexpected kernel crashes when debug information is read, increasing downtime and operational risk especially in environments with many dependent packages.
How an attack unfolds
An attacker triggers the debug proc read path on a CIFS mount where the server did not populate LinkSpeed, causing the divide error and kernel panic; no remote code execution is involved.
How to fix it
Update the Linux kernel to a version containing the fix that defaults cifs_server_iface::speed to 1 Gbps when LinkSpeed is unset; apply the patch or newer kernel release.
How to confirm the fix worked
Confirm the kernel version includes the commit that initializes speed to a sane default and test that reading cifs debug data no longer produces a divide error on connections with missing LinkSpeed.
Typical attack path
- Establish an SMB connection to a server that omits LinkSpeed in NETWORK_INTERFACE_INFO
- Trigger cifs_debug_data_proc_show via /proc/fs/cifs or equivalent debug read
- Trigger the divide instruction on the unset speed value
- Cause kernel oops and system instability
How to detect it
Review kernel logs for divide error oopses with stack traces containing cifs_debug_data_proc_show and seq_read_iter on systems with active CIFS mounts.
What your security team should do
- Prioritize kernel updates on all systems using the CIFS client module
- Monitor for oops reports involving cifs_debug_data_proc_show
- Limit exposure by restricting unnecessary SMB debug access until patched
The record
In the Linux kernel, the following vulnerability has been resolved: smb: client: fix oops due to unset link speed It isn't guaranteed that NETWORK_INTERFACE_INFO::LinkSpeed will always be set by the server, so the client must handle any values and then prevent oopses like below from happening: Oops: divide error: 0000 [#1] PREEMPT SMP KASAN NOPTI CPU: 0 UID: 0 PID: 1323 Comm: cat Not tainted 6.13.0-rc7 #2 Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.16.3-3.fc41 04/01/2014 RIP: 0010:cifs_debug_data_proc_show+0xa45/0x1460 [cifs] Code: 00 00 48 89 df e8 3b cd 1b c1 41 f6 44 24 2c 04 0f 84 50 01 00 00 48 89 ef e8 e7 d0 1b c1 49 8b 44 24 18 31 d2 49 8d 7c 24 28 <48> f7 74 24 18 48 89 c3 e8 6e cf 1b c1 41 8b 6c 24 28 49 8d 7c 24 RSP: 0018:ffffc90001817be0 EFLAGS: 00010246 RAX: 0000000000000000 RBX: ffff88811230022c RCX: ffffffffc041bd99 RDX: 0000000000000000 RSI: 0000000000000567 RDI: ffff888112300228 RBP: ffff888112300218 R08: fffff52000302f5f R09: ffffed1022fa58ac R10: ffff888117d2c566 R11: 00000000fffffffe R12: ffff888112300200 R13: 000000012a15343f R14: 0000000000000001 R15: ffff888113f2db58 FS: 00007fe27119e740(0000) GS:ffff888148600000(0000) knlGS:0000000000000000 CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 CR2: 00007fe2633c5000 CR3: 0000000124da0000 CR4: 0000000000750ef0 PKRU: 55555554 Call Trace: <TASK> ? __die_body.cold+0x19/0x27 ? die+0x2e/0x50 ? do_trap+0x159/0x1b0 ? cifs_debug_data_proc_show+0xa45/0x1460 [cifs] ? do_error_trap+0x90/0x130 ? cifs_debug_data_proc_show+0xa45/0x1460 [cifs] ? exc_divide_error+0x39/0x50 ? cifs_debug_data_proc_show+0xa45/0x1460 [cifs] ? asm_exc_divide_error+0x1a/0x20 ? cifs_debug_data_proc_show+0xa39/0x1460 [cifs] ? cifs_debug_data_proc_show+0xa45/0x1460 [cifs] ? seq_read_iter+0x42e/0x790 seq_read_iter+0x19a/0x790 proc_reg_read_iter+0xbe/0x110 ? __pfx_proc_reg_read_iter+0x10/0x10 vfs_read+0x469/0x570 ? do_user_addr_fault+0x398/0x760 ? __pfx_vfs_read+0x10/0x10 ? find_held_lock+0x8a/0xa0 ? __pfx_lock_release+0x10/0x10 ksys_read+0xd3/0x170 ? __pfx_ksys_read+0x10/0x10 ? __rcu_read_unlock+0x50/0x270 ? mark_held_locks+0x1a/0x90 do_syscall_64+0xbb/0x1d0 entry_SYSCALL_64_after_hwframe+0x77/0x7f RIP: 0033:0x7fe271288911 Code: 00 48 8b 15 01 25 10 00 f7 d8 64 89 02 b8 ff ff ff ff eb bd e8 20 ad 01 00 f3 0f 1e fa 80 3d b5 a7 10 00 00 74 13 31 c0 0f 05 <48> 3d 00 f0 ff ff 77 4f c3 66 0f 1f 44 00 00 55 48 89 e5 48 83 ec RSP: 002b:00007ffe87c079d8 EFLAGS: 00000246 ORIG_RAX: 0000000000000000 RAX: ffffffffffffffda RBX: 0000000000040000 RCX: 00007fe271288911 RDX: 0000000000040000 RSI: 00007fe2633c6000 RDI: 0000000000000003 RBP: 00007ffe87c07a00 R08: 0000000000000000 R09: 00007fe2713e6380 R10: 0000000000000022 R11: 0000000000000246 R12: 0000000000040000 R13: 00007fe2633c6000 R14: 0000000000000003 R15: 0000000000000000 </TASK> Fix this by setting cifs_server_iface::speed to a sane value (1Gbps) by default when link speed is unset.
Affected packages
| Ecosystem | Package | Introduced | Fixed |
|---|---|---|---|
| Debian:11 | linux-6.1 | 0 | 6.1.129-1~deb11u1 |
| Debian:12 | linux | 0 | No fix |
| Debian:13 | linux | 0 | No fix |
| Debian:13 | linux | 0 | 6.12.13-1 |
| Linux | Kernel | 0 | 6.1.129 |
| SUSE:Linux Enterprise High Availability Extension 15 SP6 | kernel-default | 0 | 6.4.0-150600.23.42.2 |
| SUSE:Linux Enterprise Live Patching 15 SP6 | kernel-default | 0 | 6.4.0-150600.23.42.2 |
| SUSE:Linux Enterprise Live Patching 15 SP6 | kernel-livepatch-SLE15-SP6-RT_Update_9 | 0 | 1-150600.1.3.2 |
| SUSE:Linux Enterprise Live Patching 15 SP6 | kernel-livepatch-SLE15-SP6_Update_9 | 0 | 1-150600.13.3.4 |
| SUSE:Linux Enterprise Module for Basesystem 15 SP6 | kernel-64kb | 0 | 6.4.0-150600.23.42.2 |
| SUSE:Linux Enterprise Module for Basesystem 15 SP6 | kernel-default | 0 | 6.4.0-150600.23.42.2 |
| SUSE:Linux Enterprise Module for Basesystem 15 SP6 | kernel-default-base | 0 | 6.4.0-150600.23.42.2.150600.12.18.4 |
| SUSE:Linux Enterprise Module for Basesystem 15 SP6 | kernel-source | 0 | 6.4.0-150600.23.42.1 |
| SUSE:Linux Enterprise Module for Basesystem 15 SP6 | kernel-zfcpdump | 0 | 6.4.0-150600.23.42.2 |
| SUSE:Linux Enterprise Module for Confidential Computing Technical Preview 15 SP6 | kernel-coco | 0 | 6.4.0-15061.21.coco15sp6.1 |
| SUSE:Linux Enterprise Module for Confidential Computing Technical Preview 15 SP6 | kernel-coco_debug | 0 | 6.4.0-15061.21.coco15sp6.1 |
| SUSE:Linux Enterprise Module for Confidential Computing Technical Preview 15 SP6 | kernel-source-coco | 0 | 6.4.0-15061.21.coco15sp6.1 |
| SUSE:Linux Enterprise Module for Confidential Computing Technical Preview 15 SP6 | kernel-syms-coco | 0 | 6.4.0-15061.21.coco15sp6.1 |
| SUSE:Linux Enterprise Module for Development Tools 15 SP6 | kernel-docs | 0 | 6.4.0-150600.23.42.1 |
| SUSE:Linux Enterprise Module for Development Tools 15 SP6 | kernel-obs-build | 0 | 6.4.0-150600.23.42.2 |
| SUSE:Linux Enterprise Module for Development Tools 15 SP6 | kernel-source | 0 | 6.4.0-150600.23.42.1 |
| SUSE:Linux Enterprise Module for Development Tools 15 SP6 | kernel-syms | 0 | 6.4.0-150600.23.42.1 |
| SUSE:Linux Enterprise Module for Legacy 15 SP6 | kernel-default | 0 | 6.4.0-150600.23.42.2 |
| SUSE:Linux Enterprise Module for Public Cloud 15 SP6 | kernel-azure | 0 | 6.4.0-150600.8.31.1 |
| SUSE:Linux Enterprise Module for Public Cloud 15 SP6 | kernel-source-azure | 0 | 6.4.0-150600.8.31.1 |
| SUSE:Linux Enterprise Module for Public Cloud 15 SP6 | kernel-syms-azure | 0 | 6.4.0-150600.8.31.1 |
| SUSE:Linux Enterprise Workstation Extension 15 SP6 | kernel-default | 0 | 6.4.0-150600.23.42.2 |
| SUSE:Real Time Module 15 SP6 | kernel-rt | 0 | 6.4.0-150600.10.29.1 |
| SUSE:Real Time Module 15 SP6 | kernel-rt_debug | 0 | 6.4.0-150600.10.29.1 |
| SUSE:Real Time Module 15 SP6 | kernel-source-rt | 0 | 6.4.0-150600.10.29.1 |
| SUSE:Real Time Module 15 SP6 | kernel-syms-rt | 0 | 6.4.0-150600.10.29.1 |
| Ubuntu:24.10 | linux-aws | 0 | 6.11.0-1014.15 |
| openSUSE:Leap 15.6 | dtb-aarch64 | 0 | 6.4.0-150600.23.42.1 |
| openSUSE:Leap 15.6 | kernel-64kb | 0 | 6.4.0-150600.23.42.2 |
| openSUSE:Leap 15.6 | kernel-azure | 0 | 6.4.0-150600.8.31.1 |
| openSUSE:Leap 15.6 | kernel-debug | 0 | 6.4.0-150600.23.42.2 |
| openSUSE:Leap 15.6 | kernel-default | 0 | 6.4.0-150600.23.42.2 |
| openSUSE:Leap 15.6 | kernel-default-base | 0 | 6.4.0-150600.23.42.2.150600.12.18.4 |
| openSUSE:Leap 15.6 | kernel-docs | 0 | 6.4.0-150600.23.42.1 |
| openSUSE:Leap 15.6 | kernel-kvmsmall | 0 | 6.4.0-150600.23.42.2 |
| openSUSE:Leap 15.6 | kernel-obs-build | 0 | 6.4.0-150600.23.42.2 |
| openSUSE:Leap 15.6 | kernel-obs-qa | 0 | 6.4.0-150600.23.42.1 |
| openSUSE:Leap 15.6 | kernel-rt | 0 | 6.4.0-150600.10.29.1 |
| openSUSE:Leap 15.6 | kernel-rt_debug | 0 | 6.4.0-150600.10.29.1 |
| openSUSE:Leap 15.6 | kernel-source | 0 | 6.4.0-150600.23.42.1 |
| openSUSE:Leap 15.6 | kernel-source-azure | 0 | 6.4.0-150600.8.31.1 |
| openSUSE:Leap 15.6 | kernel-source-rt | 0 | 6.4.0-150600.10.29.1 |
| openSUSE:Leap 15.6 | kernel-syms | 0 | 6.4.0-150600.23.42.1 |
| openSUSE:Leap 15.6 | kernel-syms-azure | 0 | 6.4.0-150600.8.31.1 |
| openSUSE:Leap 15.6 | kernel-syms-rt | 0 | 6.4.0-150600.10.29.1 |
| openSUSE:Leap 15.6 | kernel-zfcpdump | 0 | 6.4.0-150600.23.42.2 |
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