CVE-2025-39831

CVE-2025-39831 is a medium-severity vulnerability in Linux Linux Kernel with a CVSS 3.x base score of 5.5. It is not currently listed as actively exploited by CISA, and its EPSS exploit-prediction score is low.

Key facts

Description

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.

Frequently asked questions

What is CVE-2025-39831?
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.
How severe is CVE-2025-39831?
CVE-2025-39831 has a CVSS 3.x base score of 5.5, rated medium severity. It is exploitable over local access with low attack complexity, requires low privileges and no user interaction. Impact on confidentiality is none, integrity none, and availability high.
Is CVE-2025-39831 being actively exploited?
It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 0% (3rd percentile), an estimate of the probability of exploitation in the next 30 days.
What products are affected by CVE-2025-39831?
CVE-2025-39831 primarily affects Linux Linux Kernel. In total, 4 product configurations (CPEs) are listed as vulnerable; see the affected-products list for the exact versions.
How do I fix CVE-2025-39831?
Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround.
Does CVE-2025-39831 have an EU (EUVD) identifier?
Yes. CVE-2025-39831 is tracked in the ENISA EU Vulnerability Database (EUVD) as EUVD-2025-29583.
When was CVE-2025-39831 published?
CVE-2025-39831 was published on 2025-09-16 and last updated on 2026-06-17.

References

Affected products (4)

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