nfsd: fix stale s2s_cp_stateids IDR entry for async COPY
CVE-2026-89676 · published 11 Sept 2026
How serious is it
- Severity: critical, CVSS score 9.8 out of 10.
- No exploit prediction (EPSS) score yet.
- Not on the CISA list of exploited vulnerabilities.
- No public exploit in Exploit-DB.
Is your app affected by CVE-2026-89676?
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Who is affected
- Linux Linux: e0639dc5805a9d4faaa2c07ad98fa853b9529dd3 to < bdce362f49410b9def65d76c21f6259cd89696d8, e0639dc5805a9d4faaa2c07ad98fa853b9529dd3 to < 7aa34ea78f74e6ef60c8112635a87fc43d57f6c9, e0639dc5805a9d4faaa2c07ad98fa853b9529dd3 to < 9b4e5e9ba5ae13808b8a6d229d87c54611ba0e7a, e0639dc5805a9d4faaa2c07ad98fa853b9529dd3 to < 14b978e8d05ce018d0afbeb6611833ef91713a02
- Linux Linux: 4.20
How to check
- Find out whether you run the affected product and which version, then compare it with the versions above.
How to fix
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- Apply the vendor's update or mitigation from the references below. If there is none yet, limit exposure of the affected service until there is.
- If a vulnerable version was live, check your logs and rotate the secrets that server could read.
The advisory
In the Linux kernel, the following vulnerability has been resolved:
nfsd: fix stale s2s_cp_stateids IDR entry for async COPY
For an async COPY, nfsd4_copy() called nfs4_init_copy_state() before
dup_copy_fields(), so the s2s_cp_stateids IDR was pointed at
&u->copy->cp_stateid -- memory in the per-rqstp COMPOUND buffer that is
reused by the next request. dup_copy_fields() copies only the value into
async_copy, so the IDR slot dangled at the transient buffer for the whole
background copy. Any IDR walker then dereferences reused request memory:
the laundromat reads cs_type from it and, if the bytes look like an
expired NFS4_COPYNOTIFY_STID, follows into
refcount_dec()/idr_remove()/kfree() on garbage; manage_cpntf_state() has
the same exposure via idr_find().
Duplicate the fields first, then register the stateid on the stable
async_copy. result->cb_stateid is unchanged.
Check your whole app
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References
- git.kernel.org/stable/c/bdce362f49410b9def65d76c21f6259cd89696d8
- git.kernel.org/stable/c/7aa34ea78f74e6ef60c8112635a87fc43d57f6c9
- git.kernel.org/stable/c/9b4e5e9ba5ae13808b8a6d229d87c54611ba0e7a
- git.kernel.org/stable/c/14b978e8d05ce018d0afbeb6611833ef91713a02
- git.kernel.org/stable/c/d0beaee498e11880e72826026db0e9c9890fc114
Merged from CVE List. Last updated 26 Oct 2026. All vulnerabilities · RSS · JSON