CVE-2025-21908

CVE-2025-21908 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. The underlying weakness is classified as CWE-667.

Key facts

Description

In the Linux kernel, the following vulnerability has been resolved: NFS: fix nfs_release_folio() to not deadlock via kcompactd writeback Add PF_KCOMPACTD flag and current_is_kcompactd() helper to check for it so nfs_release_folio() can skip calling nfs_wb_folio() from kcompactd. Otherwise NFS can deadlock waiting for kcompactd enduced writeback which recurses back to NFS (which triggers writeback to NFSD via NFS loopback mount on the same host, NFSD blocks waiting for XFS's call to __filemap_get_folio): 6070.550357] INFO: task kcompactd0:58 blocked for more than 4435 seconds. {--- [58] "kcompactd0" [<0>] folio_wait_bit+0xe8/0x200 [<0>] folio_wait_writeback+0x2b/0x80 [<0>] nfs_wb_folio+0x80/0x1b0 [nfs] [<0>] nfs_release_folio+0x68/0x130 [nfs] [<0>] split_huge_page_to_list_to_order+0x362/0x840 [<0>] migrate_pages_batch+0x43d/0xb90 [<0>] migrate_pages_sync+0x9a/0x240 [<0>] migrate_pages+0x93c/0x9f0 [<0>] compact_zone+0x8e2/0x1030 [<0>] compact_node+0xdb/0x120 [<0>] kcompactd+0x121/0x2e0 [<0>] kthread+0xcf/0x100 [<0>] ret_from_fork+0x31/0x40 [<0>] ret_from_fork_asm+0x1a/0x30 ---} [[email protected]: fix build]

Frequently asked questions

What is CVE-2025-21908?
In the Linux kernel, the following vulnerability has been resolved: NFS: fix nfs_release_folio() to not deadlock via kcompactd writeback Add PF_KCOMPACTD flag and current_is_kcompactd() helper to check for it so nfs_release_folio() can skip calling nfs_wb_folio() from kcompactd. Otherwise NFS can deadlock waiting for kcompactd enduced writeback which recurses back to NFS (which triggers writeback to NFSD via NFS loopback mount on the same host, NFSD blocks waiting for XFS's call to __filemap_get_folio): 6070.550357] INFO: task kcompactd0:58 blocked for more than 4435 seconds. {--- [58] "kcompactd0" [<0>] folio_wait_bit+0xe8/0x200 [<0>] folio_wait_writeback+0x2b/0x80 [<0>] nfs_wb_folio+0x80/0x1b0 [nfs] [<0>] nfs_release_folio+0x68/0x130 [nfs] [<0>] split_huge_page_to_list_to_order+0x362/0x840 [<0>] migrate_pages_batch+0x43d/0xb90 [<0>] migrate_pages_sync+0x9a/0x240 [<0>] migrate_pages+0x93c/0x9f0 [<0>] compact_zone+0x8e2/0x1030 [<0>] compact_node+0xdb/0x120 [<0>] kcompactd+0x121/0x2e0 [<0>] kthread+0xcf/0x100 [<0>] ret_from_fork+0x31/0x40 [<0>] ret_from_fork_asm+0x1a/0x30 ---} [[email protected]: fix build]
How severe is CVE-2025-21908?
CVE-2025-21908 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-2025-21908 being actively exploited?
It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 0% (4th percentile), an estimate of the probability of exploitation in the next 30 days.
What products are affected by CVE-2025-21908?
CVE-2025-21908 primarily affects Linux Linux Kernel. In total, 6 product configurations (CPEs) are listed as vulnerable; see the affected-products list for the exact versions.
How do I fix CVE-2025-21908?
Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround.
Does CVE-2025-21908 have an EU (EUVD) identifier?
Yes. CVE-2025-21908 is tracked in the ENISA EU Vulnerability Database (EUVD) as EUVD-2025-9413.
When was CVE-2025-21908 published?
CVE-2025-21908 was published on 2025-04-01 and last updated on 2026-06-17.

References

Affected products (6)

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