CVE-2025-39831

What it is

In the Linux kernel, the following vulnerability has been resolved: fbnic: Move phylink resume out of service_task and into open/close The fbnic driver was presenting with the following locking assert coming out of a PM resume: [ 42.208116][ T164] RTNL: assertion failed at drivers/net/phy/phylink.c (2611) [ 42.208492][ T164] WARNING: CPU: 1 PID: 164 at drivers/net/phy/phylink.c:2611 phylink_resume+0x190/0x1e0 [ 42.208872][ T164] Modules linked in: [ 42.209140][ T164] CPU: 1 UID: 0 PID: 164 Comm: bash Not tainted 6.17.0-rc2-virtme #134 PREEMPT(full) [ 42.209496][ T164] Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.17.0-5.fc42 04/01/2014 [ 42.209861][ T164] RIP: 0010:phylink_resume+0x190/0x1e0 [ 42.210057][ T164] Code: 83 e5 01 0f 85 b0 fe ff ff c6 05 1c cd 3e 02 01 90 ba 33 0a 00 00 48 c7 c6 20 3a 1d a5 48 c7 c7 e0 3e 1d a5 e8 21 b8 90 fe 90 <0f> 0b 90 90 e9 86 fe ff ff e8 42 ea 1f ff e9 e2 fe ff ff 48 89 ef [ 42.210708][ T164] RSP: 0018:ffffc90000affbd8 EFLAGS: 00010296 [ 42.210983][ T164] RAX: 0000000000000000 RBX: ffff8880078d8400 RCX: 0000000000000000 [ 42.211235][ T164] RDX: 0000000000000000 RSI: 1ffffffff4f10938 RDI: 0000000000000001 [ 42.211466][ T164] RBP: 0000000000000000 R08: ffffffffa2ae79ea R09: fffffbfff4b3eb84 [ 42.211707][ T164] R10: 0000000000000003 R11: 0000000000000000 R12: ffff888007ad8000 [ 42.211997][ T164] R13: 0000000000000002 R14: ffff888006a18800 R15: ffffffffa34c59e0 [ 42.212234][ T164] FS: 00007f0dc8e39740(0000) GS:ffff88808f51f000(0000) knlGS:0000000000000000 [ 42.212505][ T164] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 [ 42.212704][ T164] CR2: 00007f0dc8e9fe10 CR3: 000000000b56d003 CR4: 0000000000772ef0 [ 42.213227][ T164] PKRU: 55555554 [ 42.213366][ T164] Call Trace: [ 42.213483][ T164] <TASK> [ 42.213565][ T164] __fbnic_pm_attach.isra.0+0x8e/0xa0 [ 42.213725][ T164] pci_reset_function+0x116/0x1d0 [ 42.213895][ T164] reset_store+0xa0/0x100 [ 42.214025][ T164] ? pci_dev_reset_attr_is_visible+0x50/0x50 [ 42.214221][ T164] ? sysfs_file_kobj+0xc1/0x1e0 [ 42.214374][ T164] ? sysfs_kf_write+0x65/0x160 [ 42.214526][ T164] kernfs_fop_write_iter+0x2f8/0x4c0 [ 42.214677][ T164] ? kernfs_vma_page_mkwrite+0x1f0/0x1f0 [ 42.214836][ T164] new_sync_write+0x308/0x6f0 [ 42.214987][ T164] ? __lock_acquire+0x34c/0x740 [ 42.215135][ T164] ? new_sync_read+0x6f0/0x6f0 [ 42.215288][ T164] ? lock_acquire.part.0+0xbc/0x260 [ 42.215440][ T164] ? ksys_write+0xff/0x200 [ 42.215590][ T164] ? perf_trace_sched_switch+0x6d0/0x6d0 [ 42.215742][ T164] vfs_write+0x65e/0xbb0 [ 42.215876][ T164] ksys_write+0xff/0x200 [ 42.215994][ T164] ? __ia32_sys_read+0xc0/0xc0 [ 42.216141][ T164] ? do_user_addr_fault+0x269/0x9f0 [ 42.216292][ T164] ? rcu_is_watching+0x15/0xd0 [ 42.216442][ T164] do_syscall_64+0xbb/0x360 [ 42.216591][ T164] entry_SYSCALL_64_after_hwframe+0x4b/0x53 [ 42.216784][ T164] RIP: 0033:0x7f0dc8ea9986 A bit of digging showed that we were invoking the phylink_resume as a part of the fbnic_up path when we were enabling the service task while not holding the RTNL lock. We should be enabling this sooner as a part of the ndo_open path and then just letting the service task come online later. This will help to enforce the correct locking and brings the phylink interface online at the same time as the network interface, instead of at a later time. I tested this on QEMU to verify this was working by putting the system to sleep using "echo mem > /sys/power/state" to put the system to sleep in the guest and then using the command "system_wakeup" in the QEMU monitor.

At a glance

Exploitability

Can be exploited locally on the machine with a low-privilege account. High risk of service disruption.

Exploit odds

0.1% chance of exploitation in the next 30 days (EPSS).

Fix

A patch, advisory or fixed version is referenced. Upgrade or apply it.

Timeline

1. 2025-09-16 14:15 UTC PublishedDisclosed publicly on CVE.org and NVD
2. 2026-10-19 21:10 UTC Last updatedMost recent change to the record

Why it ranks here

• Exploited in the wild: no, CISA does not list it.
• Exploit odds: 0.1% in the next 30 days (EPSS).
• Severity: 5.5 MEDIUM (CVSS).
• Fix: a patch or advisory is linked.

Details

Published

2025-09-16 14:15 UTC

Last modified

2026-10-19 21:10 UTC

Exploit probability

0.1% · EPSS, next 30 days

Record status

Modified

Affected

• Linux Kernel < 6.12.45
• Linux Kernel < 6.16.5
• Linux Kernel 6.17

Attack profile CVSS 3.1 · 5.5

Attack vector

Local

Complexity

Low

Privileges needed

Low

User interaction

None

Scope

Unchanged

Confidentiality

None

Integrity

None

Availability

High

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