Answer in brief
CVE-2026-89670 records a Unknown severity vulnerability in nfsd: hold rcu across localio cmpxchg retry. The current sources do not mark it as known exploited. The current feed maps Linux/Linux (generic), Linux/Linux (generic). Check affected ranges and fixed versions before updating.
Analysis pending evidence review
HOL Guard separates source facts from reviewed analysis. See the methodology.
A CVSS score is not reported in the current record. The current sources do not mark it as known exploited. Treat this as a source-backed prioritization signal, not a statement about your environment.
Analysis status
Analysis pending evidence review
Factual feed record only; HOL analysis is not approved for indexing. Read the methodology.
The current feed maps Linux/Linux (generic), Linux/Linux (generic). Check affected ranges and fixed versions before updating.
| Package | Affected range | Fixed version |
|---|---|---|
| Linux/Linuxgeneric | >=e6f7e1487ab528a6c653bd0d42812ff2942846cd <763c0bad872368304db718f79af7e93048885c67 || >=e6f7e1487ab528a6c653bd0d42812ff2942846cd <559570f91a7d4d199a72105e4980bef791f4cbf1 || >=e6f7e1487ab528a6c653bd0d42812ff2942846cd <58884694978a3d7d111edb433d7fd6a6c5af2f34 || 986a21ace186433e0397a59491646edad8c8d636 || >=6.15.3 <6.16 | 763c0bad872368304db718f79af7e93048885c67, 559570f91a7d4d199a72105e4980bef791f4cbf1, 58884694978a3d7d111edb433d7fd6a6c5af2f34, 6.16 |
| Linux/Linuxgeneric | 6.16 | Not reported |
Published upstream
Sep 11, 2026
Evidence: source:cvelist:source_dates:source-dates:recordSource modified
Sep 11, 2026
Evidence: source:cvelist:source_dates:source-dates:recordFirst seen by HOL
Sep 11, 2026
In the Linux kernel, the following vulnerability has been resolved: nfsd: hold rcu across localio cmpxchg retry nfsd_file objects are freed via call_rcu (filecache.c:296), and nfsd_file_slab is created without SLAB_TYPESAFE_BY_RCU (KMEM_CACHE(nfsd_file, 0) at filecache.c:789), so the slab page backing a freed nfsd_file becomes freely reclaimable once the RCU grace period elapses. The again: retry block in nfsd_open_local_fh() loads a pointer with cmpxchg and then calls nfsd_file_get(new) (which is refcount_inc_not_zero) without holding rcu_read_lock. The sole caller nfs_open_local_fh() drops rcu_read_lock before invoking this helper, so no outer reader-side critical section covers the load. CPU 0 (nfsd_open_local_fh) CPU 1 (nfsd_file_put_local) ----- ----- new = cmpxchg(pnf, NULL, ...) nf = xchg(pnf, NULL) nfsd_file_put(nf) last ref -> call_rcu() /* grace period elapses; slab page recycled */ nfsd_file_get(new) refcount_inc_not_zero(&new->nf_ref) /* operates on recycled memory */ A non-zero word at the nf_ref offset of the recycled object makes the refcount bump appear to succeed, and the caller then dereferences new->nf_net and new->nf_file out of freed memory. Fix by taking rcu_read_lock() immediately before the cmpxchg and releasing it on all three exits of the if (new) block: the goto-again retry, the lost-race cleanup path, and the install-succeeded path. nfsd_file_put() and nfsd_net_put() stay outside the RCU section so they remain free to block.
Quoted source text, attributed separately from HOL analysis.