CVE-2026-89707
HighCVSS 7.5Exploitation Probability (EPSS)
Low risk47th percentile - higher than 47% of all known CVEs
Summary
In the Linux kernel, nfsd_cross_mnt() jumped to the out label on a follow_down() error without releasing the path references taken by mntget() and dget(). This leaked references on each failed cross-mount, blocking umount and pinning dentries.
Risk Assessment
A path reference leak blocks filesystem unmounting and pins dentries, potentially leading to resource exhaustion and denial of service.
Recommendation
Update the Linux kernel to a version containing the fix that calls path_put(&path) before the goto out in the follow_down() error arm.
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Original NVD description (English source)
In the Linux kernel, the following vulnerability has been resolved: nfsd: release path refs on follow_down() error nfsd_cross_mnt() initializes a local struct path with mntget() and dget() before calling follow_down(). On a negative return the error arm jumps to out without releasing those references: err = follow_down(&path, follow_flags); if (err < 0) goto out; follow_down() never drops the caller's entry-time refs on any error sub-case; for example a pre-cross d_manage() failure leaves path untouched, so the mntget()/dget() taken on entry survive the call. Every other early-exit arm in nfsd_cross_mnt() (other-namespace return, IS_ERR(exp2), and the success tail after the swap) already calls path_put(&path); the err < 0 arm is the lone omission. The leak inflates mnt_count and d_count on each failed cross-mount, blocking umount and pinning dentries against the shrinker, and is reachable by any authenticated NFS client through nfsd_lookup_dentry or the NFSv4 READDIR encode path. Fix by calling path_put(&path) before the goto out in the err < 0 arm so the entry-time refs are released on all follow_down() error returns.
Vulnerability data from NVD (NIST) · CISA KEV · EPSS