CVE-2026-53026: NFSD: fix nfs4_file access extra count in nfsd4_add_rdaccess_to_wrdeleg

Severity: high (CVSS 7.5 v3.1)
Exploited in the wild: not listed in CISA KEV
EPSS: 0.4% probability of exploitation in the next 30 days
Public exploit or detection template: none known
Published: 2026-06-24 · updated 2026-07-15

Description

In the Linux kernel, the following vulnerability has been resolved: NFSD: fix nfs4_file access extra count in nfsd4_add_rdaccess_to_wrdeleg In nfsd4_add_rdaccess_to_wrdeleg, if fp->fi_fds[O_RDONLY] is already set by another thread, __nfs4_file_get_access should not be called to increment the nfs4_file access count since that was already done by the thread that added READ access to the file. The extra fi_access count in nfs4_file can prevent the corresponding nfsd_file from being freed. When stopping nfs-server service, these extra access counts trigger a BUG in kmem_cache_destroy() that shows nfsd_file object remaining on __kmem_cache_shutdown. This problem can be reproduced by running the Git project's test suite over NFS.

Affected products

Linux kernel: from 6.18.4 before 6.18.33; from 6.19.1 before 7.0.10; 6.19, 6.19-rc4, 6.19-rc5, 6.19-rc6, 6.19-rc7, 6.19-rc8 — fixed in 6.18.33, 7.0.10

How to fix

Upgrade to a fixed version: Linux kernel 6.18.33, 7.0.10. Check the vendor advisory for mitigations.

References

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