CVE-2026-93229 nfsd: add missing read barrier to rpc_status_get dumpit seqcount retry
A missing memory barrier in the Linux kernel NFS server allows concurrent data modification to be observed inconsistently, potentially leading to incorrect data reads.
- Exploited in the wild
- Not known
- Login needed
- Any signed-in user
- Attackable
- Local or same network only
- Victim action needed
- Not needed
- Fix
- Available
What is CVE-2026-93229?
CVE-2026-93229 is a high-severity vulnerability in Linux, published on 24 Sep 2026. It can only be exploited from the same machine or local network, with no action from the victim.
Official description
In the Linux kernel, the following vulnerability has been resolved:
nfsd: add missing read barrier to rpc_status_get dumpit seqcount retry
The hand-rolled seqcount-like protocol in nfsd_nl_rpc_status_get_dumpit() is missing a read memory barrier (smp_rmb) before its second counter check. The standard kernel read_seqcount_retry() includes smp_rmb() to ensure that all data reads complete before the counter is re-checked.
Without this barrier, on weakly-ordered architectures (ARM, POWER), the CPU may reorder field reads past the second counter check, making the retry logic ineffective: it could observe a consistent counter pair while reading fields that have been concurrently modified by the writer.
Add smp_rmb() before the second counter check to order the field reads ahead of it, matching the barrier semantics of the standard seqcount read-side. The begin-side smp_load_acquire() already pairs with the smp_store_release() in nfsd_dispatch(); with the smp_rmb() now ordering the field reads, the retry check no longer needs acquire semantics and reads the counter with a plain READ_ONCE(), as read_seqcount_retry() does.
[ cel: Use READ_ONCE instead of smp_load_acquire() ]
Which versions are affected by CVE-2026-93229?
How do I fix CVE-2026-93229?
Apply the vendor's patch.
Is CVE-2026-93229 being exploited?
There is no known exploitation of CVE-2026-93229 in the wild and no public exploit code.
Sources
Also known as BELL-CVE-2026-93229, DEBIAN-CVE-2026-93229, GHSA-fg62-2q3c-3w5h, UBUNTU-CVE-2026-93229.