CVE-2026-89665 (GCVE-0-2026-89665)
Vulnerability from cvelistv5 – Published: 2026-09-11 19:45 – Updated: 2026-10-19 08:50
VLAI
EPSS
VEX
Title
nfsd: reject out-of-range useconds in NFSv2 SETATTR/CREATE
Summary
In the Linux kernel, the following vulnerability has been resolved:
nfsd: reject out-of-range useconds in NFSv2 SETATTR/CREATE
The NFSv2 sattr decoder converts the wire useconds to nanoseconds in
svcxdr_decode_sattr():
iap->ia_atime.tv_nsec = tmp2 * NSEC_PER_USEC;
tmp2 is a u32 and NSEC_PER_USEC is 1000, so the product is computed in
unsigned long. On ILP32 that is 32 bits, and an out-of-range useconds
value such as 4294968 wraps to tv_nsec == 704. The corruption therefore
happens during decode, before any proc function can inspect the value,
and a later range check on tv_nsec would see an in-range result and
accept it. Rejecting in the decoder yields an RPC GARBAGE_ARGS reply.
NFSv2 defines no NFSERR_INVAL, so there is no NFS-level status to return
for a malformed time argument, and the check cannot move to the proc
function the way the v3/v4 nsec range checks do.
Guard the raw useconds before the multiplication and reject values
greater than 1000000. useconds == 1000000 is kept: it is the Sun
convention for "set to the current server time", and the in-tree Linux
NFSv2 client emits it in both the atime and the mtime field for a plain
touch / utimes(file, NULL) (see encode_sattr() and
xdr_encode_current_server_time() in fs/nfs/nfs2xdr.c). Rejecting 1000000
would turn that common operation into a hard decode failure for both
SETATTR and CREATE. 1000000 * NSEC_PER_USEC is 10^9, which does not wrap
on ILP32, so the Sun convention value passes through safely. Only
genuinely out-of-range values (> 1000000) are rejected. The atime and
mtime guards are therefore symmetric.
The decoder only applied the Sun convention in the mtime block, which
clears ATTR_ATIME_SET|ATTR_MTIME_SET when mtime useconds == 1000000. If a
client puts 1000000 in the atime field but not in the mtime field, the
atime block stored an out-of-range tv_nsec (10^9) and left ATTR_ATIME_SET
set, so the bogus value reached the filesystem. Apply the convention in
the atime block as well, clearing ATTR_ATIME_SET so the server uses its
current time and ignores the value. Only ATTR_ATIME_SET is cleared there.
The mtime block keeps its existing behavior, where 1000000 means "set
both atime and mtime to now".
[ cel: various tweaks, addenda, and clean-ups ]
Severity
8.2 (High)
SSVC
Exploitation: none
Automatable: yes
Technical Impact: partial
CISA Coordinator · CISA-ADP (v2.0.3)
Decision recorded 2026-10-16 19:25 UTC
Assigner
References
8 references
Impacted products
2 products
| Vendor | Product | Version | CPE status | |
|---|---|---|---|---|
| Linux | Linux |
Affected:
1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 , < cdc3299f7072777b09c9582a3b8b65bb163ddcf3
(git)
Affected: 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 , < 09a79d9ab35a39603c834e8f6333603292f9c816 (git) Affected: 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 , < 5296a2442d12d45d6eea7b4d3ec3ffecc1821cac (git) Affected: 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 , < 1db456ffc22e045f49f7b9e62415a26b3f33f200 (git) Affected: 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 , < a937dd1aa2d92291fe0a1860d17e90d8f206cd22 (git) Affected: 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 , < ad02d095439f89cbd6629420c7e3ba476457b83b (git) Affected: 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 , < 1195483965a5f63d2dde18054ec7e50a23b9071c (git) Affected: 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 , < 26709c8ffe73772eb69e68d553ac71d91228dccc (git) |
guessed | |
| Linux | Linux |
Affected:
2.6.12
Unaffected: 0 , < 2.6.12 (semver) Unaffected: 5.10.270 , ≤ 5.10.* (semver) Unaffected: 5.15.221 , ≤ 5.15.* (semver) Unaffected: 6.1.188 , ≤ 6.1.* (semver) Unaffected: 6.6.157 , ≤ 6.6.* (semver) Unaffected: 6.12.109 , ≤ 6.12.* (semver) Unaffected: 6.18.50 , ≤ 6.18.* (semver) Unaffected: 7.2.4 , ≤ 7.2.* (semver) Unaffected: 7.3 , ≤ * (original_commit_for_fix) |
guessed |
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"value": "In the Linux kernel, the following vulnerability has been resolved:\n\nnfsd: reject out-of-range useconds in NFSv2 SETATTR/CREATE\n\nThe NFSv2 sattr decoder converts the wire useconds to nanoseconds in\nsvcxdr_decode_sattr():\n\n\tiap-\u003eia_atime.tv_nsec = tmp2 * NSEC_PER_USEC;\n\ntmp2 is a u32 and NSEC_PER_USEC is 1000, so the product is computed in\nunsigned long. On ILP32 that is 32 bits, and an out-of-range useconds\nvalue such as 4294968 wraps to tv_nsec == 704. The corruption therefore\nhappens during decode, before any proc function can inspect the value,\nand a later range check on tv_nsec would see an in-range result and\naccept it. Rejecting in the decoder yields an RPC GARBAGE_ARGS reply.\nNFSv2 defines no NFSERR_INVAL, so there is no NFS-level status to return\nfor a malformed time argument, and the check cannot move to the proc\nfunction the way the v3/v4 nsec range checks do.\n\nGuard the raw useconds before the multiplication and reject values\ngreater than 1000000. useconds == 1000000 is kept: it is the Sun\nconvention for \"set to the current server time\", and the in-tree Linux\nNFSv2 client emits it in both the atime and the mtime field for a plain\ntouch / utimes(file, NULL) (see encode_sattr() and\nxdr_encode_current_server_time() in fs/nfs/nfs2xdr.c). Rejecting 1000000\nwould turn that common operation into a hard decode failure for both\nSETATTR and CREATE. 1000000 * NSEC_PER_USEC is 10^9, which does not wrap\non ILP32, so the Sun convention value passes through safely. Only\ngenuinely out-of-range values (\u003e 1000000) are rejected. The atime and\nmtime guards are therefore symmetric.\n\nThe decoder only applied the Sun convention in the mtime block, which\nclears ATTR_ATIME_SET|ATTR_MTIME_SET when mtime useconds == 1000000. If a\nclient puts 1000000 in the atime field but not in the mtime field, the\natime block stored an out-of-range tv_nsec (10^9) and left ATTR_ATIME_SET\nset, so the bogus value reached the filesystem. Apply the convention in\nthe atime block as well, clearing ATTR_ATIME_SET so the server uses its\ncurrent time and ignores the value. Only ATTR_ATIME_SET is cleared there.\nThe mtime block keeps its existing behavior, where 1000000 means \"set\nboth atime and mtime to now\".\n\n[ cel: various tweaks, addenda, and clean-ups ]"
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"value": "AV:N - The bug is in nfsd\u0027s NFSv2 XDR decoder svcxdr_decode_sattr(), used by SETATTR, CREATE, and SYMLINK on the in-kernel NFS server (TCP/UDP 2049); a remote client triggers it by sending those procedures with an out-of-range sattr useconds field.\nAC:L - The attacker fully controls the sattr atime/mtime useconds fields and can deterministically supply a value greater than 1000000, or 1000000 in atime only; the ILP32 multiply wrap and the LP64 out-of-range nsec store need no race or other condition the attacker cannot influence.\nPR:N - Typical nfsd deployments accept AUTH_SYS/AUTH_NULL on reachable exports, so a network peer can obtain a filehandle and assert an owner UID without verified credentials; NFSv2 SETATTR/CREATE then applies the decoded timestamps under those unauthenticated credentials.\nUI:N - The attacker alone looks up a filehandle and issues SETATTR or CREATE with a crafted useconds value; no victim user action is required beyond nfsd already exporting a writable filesystem with NFSv2 enabled.\nS:U - Impact is confined to the NFS server\u0027s own kernel and filesystem inode timestamp metadata under the same OS security authority; there is no VM escape, IOMMU bypass, or other cross-boundary effect.\nC:N - The decoder only converts a client useconds field into ia_atime/ia_mtime.tv_nsec and later writes it via setattr; there is no out-of-bounds read, use-after-free, or other kernel-memory disclosure primitive.\nI:H - Out-of-range nsec is not rejected and notify_change()/timestamp_truncate() store it verbatim on nanosecond filesystems, so ext4_encode_extra_time() overflows the extra field and clobbers epoch bits and XFS mis-stores the timestamp, persistently corrupting on-disk inode metadata; when uncertain versus Low, High is required.\nA:L - Corrupted on-disk timestamps can cause xfs scrub to flag inodes corrupt and can break mtime-based tools on the exported file, degrading service around that inode. No oops, panic, hang, or other kernel crash was found on this path, so availability loss is partial rather than total."
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"value": "In the Linux kernel, the following vulnerability has been resolved:\n\nnfsd: reject out-of-range useconds in NFSv2 SETATTR/CREATE\n\nThe NFSv2 sattr decoder converts the wire useconds to nanoseconds in\nsvcxdr_decode_sattr():\n\n\tiap-\u003eia_atime.tv_nsec = tmp2 * NSEC_PER_USEC;\n\ntmp2 is a u32 and NSEC_PER_USEC is 1000, so the product is computed in\nunsigned long. On ILP32 that is 32 bits, and an out-of-range useconds\nvalue such as 4294968 wraps to tv_nsec == 704. The corruption therefore\nhappens during decode, before any proc function can inspect the value,\nand a later range check on tv_nsec would see an in-range result and\naccept it. Rejecting in the decoder yields an RPC GARBAGE_ARGS reply.\nNFSv2 defines no NFSERR_INVAL, so there is no NFS-level status to return\nfor a malformed time argument, and the check cannot move to the proc\nfunction the way the v3/v4 nsec range checks do.\n\nGuard the raw useconds before the multiplication and reject values\ngreater than 1000000. useconds == 1000000 is kept: it is the Sun\nconvention for \"set to the current server time\", and the in-tree Linux\nNFSv2 client emits it in both the atime and the mtime field for a plain\ntouch / utimes(file, NULL) (see encode_sattr() and\nxdr_encode_current_server_time() in fs/nfs/nfs2xdr.c). Rejecting 1000000\nwould turn that common operation into a hard decode failure for both\nSETATTR and CREATE. 1000000 * NSEC_PER_USEC is 10^9, which does not wrap\non ILP32, so the Sun convention value passes through safely. Only\ngenuinely out-of-range values (\u003e 1000000) are rejected. The atime and\nmtime guards are therefore symmetric.\n\nThe decoder only applied the Sun convention in the mtime block, which\nclears ATTR_ATIME_SET|ATTR_MTIME_SET when mtime useconds == 1000000. If a\nclient puts 1000000 in the atime field but not in the mtime field, the\natime block stored an out-of-range tv_nsec (10^9) and left ATTR_ATIME_SET\nset, so the bogus value reached the filesystem. Apply the convention in\nthe atime block as well, clearing ATTR_ATIME_SET so the server uses its\ncurrent time and ignores the value. Only ATTR_ATIME_SET is cleared there.\nThe mtime block keeps its existing behavior, where 1000000 means \"set\nboth atime and mtime to now\".\n\n[ cel: various tweaks, addenda, and clean-ups ]"
}
],
"id": "CVE-2026-89665",
"lastModified": "2026-10-19T09:18:04.497",
"metrics": {
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"integrityImpact": "HIGH",
"privilegesRequired": "NONE",
"scope": "UNCHANGED",
"userInteraction": "NONE",
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"current_release_date": "2026-10-21T14:33:49+00:00",
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"source": "Red Hat CSAF VEX",
"status": "final",
"title": "kernel: nfsd: reject out-of-range useconds in NFSv2 SETATTR/CREATE",
"url": "https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-89665.json",
"version": "3"
},
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"shortName": "CISA-ADP"
},
"title": "CISA ADP Vulnrichment"
}
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"cna": {
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"value": "In the Linux kernel, the following vulnerability has been resolved:\n\nnfsd: reject out-of-range useconds in NFSv2 SETATTR/CREATE\n\nThe NFSv2 sattr decoder converts the wire useconds to nanoseconds in\nsvcxdr_decode_sattr():\n\n\tiap-\u003eia_atime.tv_nsec = tmp2 * NSEC_PER_USEC;\n\ntmp2 is a u32 and NSEC_PER_USEC is 1000, so the product is computed in\nunsigned long. On ILP32 that is 32 bits, and an out-of-range useconds\nvalue such as 4294968 wraps to tv_nsec == 704. The corruption therefore\nhappens during decode, before any proc function can inspect the value,\nand a later range check on tv_nsec would see an in-range result and\naccept it. Rejecting in the decoder yields an RPC GARBAGE_ARGS reply.\nNFSv2 defines no NFSERR_INVAL, so there is no NFS-level status to return\nfor a malformed time argument, and the check cannot move to the proc\nfunction the way the v3/v4 nsec range checks do.\n\nGuard the raw useconds before the multiplication and reject values\ngreater than 1000000. useconds == 1000000 is kept: it is the Sun\nconvention for \"set to the current server time\", and the in-tree Linux\nNFSv2 client emits it in both the atime and the mtime field for a plain\ntouch / utimes(file, NULL) (see encode_sattr() and\nxdr_encode_current_server_time() in fs/nfs/nfs2xdr.c). Rejecting 1000000\nwould turn that common operation into a hard decode failure for both\nSETATTR and CREATE. 1000000 * NSEC_PER_USEC is 10^9, which does not wrap\non ILP32, so the Sun convention value passes through safely. Only\ngenuinely out-of-range values (\u003e 1000000) are rejected. The atime and\nmtime guards are therefore symmetric.\n\nThe decoder only applied the Sun convention in the mtime block, which\nclears ATTR_ATIME_SET|ATTR_MTIME_SET when mtime useconds == 1000000. If a\nclient puts 1000000 in the atime field but not in the mtime field, the\natime block stored an out-of-range tv_nsec (10^9) and left ATTR_ATIME_SET\nset, so the bogus value reached the filesystem. Apply the convention in\nthe atime block as well, clearing ATTR_ATIME_SET so the server uses its\ncurrent time and ignores the value. Only ATTR_ATIME_SET is cleared there.\nThe mtime block keeps its existing behavior, where 1000000 means \"set\nboth atime and mtime to now\".\n\n[ cel: various tweaks, addenda, and clean-ups ]"
}
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"value": "AV:N - The bug is in nfsd\u0027s NFSv2 XDR decoder svcxdr_decode_sattr(), used by SETATTR, CREATE, and SYMLINK on the in-kernel NFS server (TCP/UDP 2049); a remote client triggers it by sending those procedures with an out-of-range sattr useconds field.\nAC:L - The attacker fully controls the sattr atime/mtime useconds fields and can deterministically supply a value greater than 1000000, or 1000000 in atime only; the ILP32 multiply wrap and the LP64 out-of-range nsec store need no race or other condition the attacker cannot influence.\nPR:N - Typical nfsd deployments accept AUTH_SYS/AUTH_NULL on reachable exports, so a network peer can obtain a filehandle and assert an owner UID without verified credentials; NFSv2 SETATTR/CREATE then applies the decoded timestamps under those unauthenticated credentials.\nUI:N - The attacker alone looks up a filehandle and issues SETATTR or CREATE with a crafted useconds value; no victim user action is required beyond nfsd already exporting a writable filesystem with NFSv2 enabled.\nS:U - Impact is confined to the NFS server\u0027s own kernel and filesystem inode timestamp metadata under the same OS security authority; there is no VM escape, IOMMU bypass, or other cross-boundary effect.\nC:N - The decoder only converts a client useconds field into ia_atime/ia_mtime.tv_nsec and later writes it via setattr; there is no out-of-bounds read, use-after-free, or other kernel-memory disclosure primitive.\nI:H - Out-of-range nsec is not rejected and notify_change()/timestamp_truncate() store it verbatim on nanosecond filesystems, so ext4_encode_extra_time() overflows the extra field and clobbers epoch bits and XFS mis-stores the timestamp, persistently corrupting on-disk inode metadata; when uncertain versus Low, High is required.\nA:L - Corrupted on-disk timestamps can cause xfs scrub to flag inodes corrupt and can break mtime-based tools on the exported file, degrading service around that inode. No oops, panic, hang, or other kernel crash was found on this path, so availability loss is partial rather than total."
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Experimental. This forecast is provided for visualization only and may change without notice. Do not use it for operational decisions.
Forecast uses a logistic model when the trend is rising, or an exponential decay model when the trend is falling. Fitted via linearized least squares.
Sightings
| Author | Source | Type | Date | Other |
|---|
Nomenclature
- Seen: The vulnerability was mentioned, discussed, or observed by the user.
- Confirmed: The vulnerability has been validated from an analyst's perspective.
- Published Proof of Concept: A public proof of concept is available for this vulnerability.
- Exploited: The vulnerability was observed as exploited by the user who reported the sighting.
- Patched: The vulnerability was observed as successfully patched by the user who reported the sighting.
- Not exploited: The vulnerability was not observed as exploited by the user who reported the sighting.
- Not confirmed: The user expressed doubt about the validity of the vulnerability.
- Not patched: The vulnerability was not observed as successfully patched by the user who reported the sighting.
Vulnerability timeline
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The MITRE ATT&CK techniques below are AI-generated suggestions, inferred from the description of the
vulnerability by the CIRCL/vulnerability-attack-technique-classification-roberta-base
model, served locally by ML-Gateway.
They have not been verified by an analyst and are provided for guidance only.
The approach is described in our paper Mapping CVEs to MITRE ATT&CK Techniques: A Curated Gold-Set Classifier and the Limits of LLM-Assisted Label Expansion.
Browse all ATT&CK techniques and the vulnerabilities related to each.
The approach is described in our paper Mapping CVEs to MITRE ATT&CK Techniques: A Curated Gold-Set Classifier and the Limits of LLM-Assisted Label Expansion.
Browse all ATT&CK techniques and the vulnerabilities related to each.
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Related by attack behaviour
Vulnerabilities whose description is nearest to this one in the vector space of the CIRCL/vulnerability-attack-technique-biencoder model. This is a similarity search over the bi-encoder space (plain cosine), not a classification, and it has no measured accuracy.