CVE-2026-89713 (GCVE-0-2026-89713)
Vulnerability from cvelistv5 – Published: 2026-09-11 19:46 – Updated: 2026-10-30 12:32
VLAI
EPSS
VEX
Title
NFSD: check truncate permission under inode lock
Summary
In the Linux kernel, the following vulnerability has been resolved:
NFSD: check truncate permission under inode lock
nfsd_setattr() checks whether a size update needs NFSD_MAY_TRUNC
before it takes inode_lock(). The comparison uses the file size sampled
by that unlocked read, but the actual ATTR_SIZE update is applied later
under inode_lock() by notify_change().
This leaves a TOCTOU window for append-only files. If a client sends a
SETATTR that does not shrink the file at the time of the unlocked
sample, a concurrent append can extend the file before nfsd_setattr()
takes inode_lock(). notify_change() then applies a real truncation
without the NFSD_MAY_TRUNC check that rejects IS_APPEND(inode). The VFS
truncate syscall paths perform their own append-only checks before
calling notify_change(), so NFSD must make this decision against the
locked size it is about to change.
Split the write-count acquisition from the truncation permission check.
Keep get_write_access() before the locked setattr work, then recheck
whether the requested size is below i_size_read(inode) after inode_lock()
has been acquired and before notify_change(ATTR_SIZE). This also avoids
the plain unlocked inode->i_size load.
Severity
9.1 (Critical)
SSVC
Exploitation: none
Automatable: yes
Technical Impact: partial
CISA Coordinator · CISA-ADP (v2.0.3)
Decision recorded 2026-10-16 19:26 UTC
Assigner
References
6 references
Impacted products
2 products
| Vendor | Product | Version | CPE status | |
|---|---|---|---|---|
| Linux | Linux |
Affected:
783112f7401ff449d979530209b3f6c2594fdb4e , < 0669861a2e8e2bdb9c1149417d8ad821996ae4fe
(git)
Affected: 783112f7401ff449d979530209b3f6c2594fdb4e , < 52d0c5bdfe232c9974d4b11f97078b9c7814f05d (git) Affected: 783112f7401ff449d979530209b3f6c2594fdb4e , < 3afa17d93ba8c925f49370c816c6dae5112d8c24 (git) Affected: 783112f7401ff449d979530209b3f6c2594fdb4e , < d8352da196349182e1afd5a93308256cddc0a97d (git) Affected: 783112f7401ff449d979530209b3f6c2594fdb4e , < 44086254479035de42ca3d286ecf25521d4e6325 (git) Affected: 783112f7401ff449d979530209b3f6c2594fdb4e , < b778e0e0a16759f22a70579c3cf8d254a40d4a7f (git) Affected: 604a3c407026d6162d15300478e63f901e435efc (git) Affected: cc4d5dc73841b98d33cdfb9822d70b0aac4beca5 (git) Affected: 3ee4f442e5b37a537297b812557b1163f96b5399 (git) Affected: a3c6cbc4eac4473ed5461d5faae2794d3e5c0e44 (git) Affected: 982898d7f97a35447403c3fcecc0d96c646ce101 (git) Affected: 3.2.89 , < 3.3 (semver) Affected: 3.16.44 , < 3.17 (semver) Affected: 4.4.53 , < 4.5 (semver) Affected: 4.9.14 , < 4.10 (semver) Affected: 4.10.2 , < 4.11 (semver) |
guessed | |
| Linux | Linux |
Affected:
4.11
Unaffected: 0 , < 4.11 (semver) Unaffected: 6.1.191 , ≤ 6.1.* (semver) Unaffected: 6.6.160 , ≤ 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: check truncate permission under inode lock\n\nnfsd_setattr() checks whether a size update needs NFSD_MAY_TRUNC\nbefore it takes inode_lock(). The comparison uses the file size sampled\nby that unlocked read, but the actual ATTR_SIZE update is applied later\nunder inode_lock() by notify_change().\n\nThis leaves a TOCTOU window for append-only files. If a client sends a\nSETATTR that does not shrink the file at the time of the unlocked\nsample, a concurrent append can extend the file before nfsd_setattr()\ntakes inode_lock(). notify_change() then applies a real truncation\nwithout the NFSD_MAY_TRUNC check that rejects IS_APPEND(inode). The VFS\ntruncate syscall paths perform their own append-only checks before\ncalling notify_change(), so NFSD must make this decision against the\nlocked size it is about to change.\n\nSplit the write-count acquisition from the truncation permission check.\nKeep get_write_access() before the locked setattr work, then recheck\nwhether the requested size is below i_size_read(inode) after inode_lock()\nhas been acquired and before notify_change(ATTR_SIZE). This also avoids\nthe plain unlocked inode-\u003ei_size load."
}
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"id": "CVE-2026-89713",
"lastModified": "2026-10-30T13:20:27.270",
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"baseSeverity": "CRITICAL",
"confidentialityImpact": "NONE",
"integrityImpact": "HIGH",
"privilegesRequired": "NONE",
"scope": "UNCHANGED",
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"url": "https://git.kernel.org/stable/c/0669861a2e8e2bdb9c1149417d8ad821996ae4fe"
},
{
"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
"url": "https://git.kernel.org/stable/c/3afa17d93ba8c925f49370c816c6dae5112d8c24"
},
{
"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
"url": "https://git.kernel.org/stable/c/44086254479035de42ca3d286ecf25521d4e6325"
},
{
"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
"url": "https://git.kernel.org/stable/c/52d0c5bdfe232c9974d4b11f97078b9c7814f05d"
},
{
"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
"url": "https://git.kernel.org/stable/c/b778e0e0a16759f22a70579c3cf8d254a40d4a7f"
},
{
"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
"url": "https://git.kernel.org/stable/c/d8352da196349182e1afd5a93308256cddc0a97d"
}
],
"sourceIdentifier": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
"vulnStatus": "Received"
}
},
"redhat_vex": {
"aggregate_severity": "Important",
"current_release_date": "2026-11-05T00:01:02+00:00",
"cve": "CVE-2026-89713",
"id": "CVE-2026-89713",
"initial_release_date": "2026-09-11T00:00:00+00:00",
"product_status:known_affected": "186",
"product_status:known_not_affected": "14",
"source": "Red Hat CSAF VEX",
"status": "final",
"title": "kernel: NFSD: check truncate permission under inode lock",
"url": "https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-89713.json",
"version": "3"
},
"vulnrichment": {
"containers": {
"adp": [
{
"metrics": [
{
"other": {
"content": {
"id": "CVE-2026-89713",
"options": [
{
"Exploitation": "none"
},
{
"Automatable": "yes"
},
{
"Technical Impact": "partial"
}
],
"role": "CISA Coordinator",
"timestamp": "2026-10-16T19:26:29.958634Z",
"version": "2.0.3"
},
"type": "ssvc"
}
}
],
"providerMetadata": {
"dateUpdated": "2026-10-16T19:26:30.995Z",
"orgId": "134c704f-9b21-4f2e-91b3-4a467353bcc0",
"shortName": "CISA-ADP"
},
"title": "CISA ADP Vulnrichment"
}
],
"cna": {
"affected": [
{
"defaultStatus": "unaffected",
"product": "Linux",
"programFiles": [
"fs/nfsd/vfs.c"
],
"repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
"vendor": "Linux",
"versions": [
{
"lessThan": "0669861a2e8e2bdb9c1149417d8ad821996ae4fe",
"status": "affected",
"version": "783112f7401ff449d979530209b3f6c2594fdb4e",
"versionType": "git"
},
{
"lessThan": "52d0c5bdfe232c9974d4b11f97078b9c7814f05d",
"status": "affected",
"version": "783112f7401ff449d979530209b3f6c2594fdb4e",
"versionType": "git"
},
{
"lessThan": "3afa17d93ba8c925f49370c816c6dae5112d8c24",
"status": "affected",
"version": "783112f7401ff449d979530209b3f6c2594fdb4e",
"versionType": "git"
},
{
"lessThan": "d8352da196349182e1afd5a93308256cddc0a97d",
"status": "affected",
"version": "783112f7401ff449d979530209b3f6c2594fdb4e",
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{
"lessThan": "44086254479035de42ca3d286ecf25521d4e6325",
"status": "affected",
"version": "783112f7401ff449d979530209b3f6c2594fdb4e",
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},
{
"lessThan": "b778e0e0a16759f22a70579c3cf8d254a40d4a7f",
"status": "affected",
"version": "783112f7401ff449d979530209b3f6c2594fdb4e",
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},
{
"status": "affected",
"version": "604a3c407026d6162d15300478e63f901e435efc",
"versionType": "git"
},
{
"status": "affected",
"version": "cc4d5dc73841b98d33cdfb9822d70b0aac4beca5",
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{
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{
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},
{
"status": "affected",
"version": "982898d7f97a35447403c3fcecc0d96c646ce101",
"versionType": "git"
},
{
"lessThan": "3.3",
"status": "affected",
"version": "3.2.89",
"versionType": "semver"
},
{
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"status": "affected",
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},
{
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"status": "affected",
"version": "4.4.53",
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},
{
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"status": "affected",
"version": "4.9.14",
"versionType": "semver"
},
{
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"status": "affected",
"version": "4.10.2",
"versionType": "semver"
}
]
},
{
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"product": "Linux",
"programFiles": [
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],
"repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
"vendor": "Linux",
"versions": [
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"version": "4.11"
},
{
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"status": "unaffected",
"version": "0",
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},
{
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"status": "unaffected",
"version": "6.1.191",
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{
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"status": "unaffected",
"version": "6.6.160",
"versionType": "semver"
},
{
"lessThanOrEqual": "6.12.*",
"status": "unaffected",
"version": "6.12.109",
"versionType": "semver"
},
{
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"status": "unaffected",
"version": "6.18.50",
"versionType": "semver"
},
{
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"status": "unaffected",
"version": "7.2.4",
"versionType": "semver"
},
{
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"status": "unaffected",
"version": "7.3",
"versionType": "original_commit_for_fix"
}
]
}
],
"cpeApplicability": [
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"vulnerable": true
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"versionEndExcluding": "7.2.4",
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},
{
"criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
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},
{
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"value": "In the Linux kernel, the following vulnerability has been resolved:\n\nNFSD: check truncate permission under inode lock\n\nnfsd_setattr() checks whether a size update needs NFSD_MAY_TRUNC\nbefore it takes inode_lock(). The comparison uses the file size sampled\nby that unlocked read, but the actual ATTR_SIZE update is applied later\nunder inode_lock() by notify_change().\n\nThis leaves a TOCTOU window for append-only files. If a client sends a\nSETATTR that does not shrink the file at the time of the unlocked\nsample, a concurrent append can extend the file before nfsd_setattr()\ntakes inode_lock(). notify_change() then applies a real truncation\nwithout the NFSD_MAY_TRUNC check that rejects IS_APPEND(inode). The VFS\ntruncate syscall paths perform their own append-only checks before\ncalling notify_change(), so NFSD must make this decision against the\nlocked size it is about to change.\n\nSplit the write-count acquisition from the truncation permission check.\nKeep get_write_access() before the locked setattr work, then recheck\nwhether the requested size is below i_size_read(inode) after inode_lock()\nhas been acquired and before notify_change(ATTR_SIZE). This also avoids\nthe plain unlocked inode-\u003ei_size load."
}
],
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"baseSeverity": "CRITICAL",
"vectorString": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:H",
"version": "3.1"
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"lang": "en",
"value": "AV:N - nfsd_setattr() is reached from in-kernel nfsd NFSv2/v3 SETATTR and NFSv4 SETATTR (including ONE_STATEID) over TCP/UDP 2049, so a remote client triggers the TOCTOU without local shell access.\nAC:L - The attacker drives both sides of the race by issuing concurrent SETATTR size RPCs, or racing SETATTR against O_APPEND writes they perform themselves; a non-shrinking unlocked i_size sample then becomes a real truncate under inode_lock. No victim-only layout is required.\nPR:N - Default nfsd exports accept AUTH_SYS and AUTH_NULL with no cryptographic authentication, so the client asserts uid/gid. ATTR_SIZE uses fh_verify(NFSD_MAY_WRITE|NFSD_MAY_OWNER_OVERRIDE), which is satisfied by spoofing the file owner\u0027s uid.\nUI:N - The attacking NFS client sends SETATTR itself. No administrator or end-user action on the server is required beyond nfsd already serving a writable export.\nS:U - The skipped IS_APPEND check and the resulting notify_change(ATTR_SIZE) truncate affect only the exported filesystem in the same kernel security authority as nfsd. This is not a VM, IOMMU, or sandbox escape.\nC:N - The bug only omits NFSD_MAY_TRUNC for IS_APPEND before a locked size update. It does not read kernel memory, leak pointers, or disclose file contents beyond ordinary authorized NFS access.\nI:H - Winning the TOCTOU lets notify_change() apply ATTR_SIZE to an IS_APPEND inode, bypassing the append-only truncation ban that VFS truncate/ftruncate enforce, so a remote client can destroy data that chattr +a is meant to keep immutable, including concurrent log and audit appends.\nA:H - Unauthorized truncation of append-only operational logs, databases, or other files that services depend on can persistently destroy that live content and deny use of it until restored, and the attacker can repeat the race at will against further files."
}
]
}
],
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"orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
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},
{
"url": "https://git.kernel.org/stable/c/b778e0e0a16759f22a70579c3cf8d254a40d4a7f"
}
],
"title": "NFSD: check truncate permission under inode lock",
"x_generator": {
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}
}
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"cveMetadata": {
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"cveId": "CVE-2026-89713",
"datePublished": "2026-09-11T19:46:27.752Z",
"dateReserved": "2026-09-11T19:38:34.751Z",
"dateUpdated": "2026-10-30T12:32:48.688Z",
"state": "PUBLISHED"
},
"dataType": "CVE_RECORD",
"dataVersion": "5.2"
}
}
}
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Drag nodes to arrange them. Double-click a related vulnerability to open it, or a source to visit its link. The Physics button on the left tunes the layout and the simulation; the legend at the bottom left hides or shows nodes by kind and by sighting type.
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
Sightings and recorded dates, grouped by day · UTC
How durations are calculated
Following the VTEM framework (Black Hat USA 2015), time to patch starts when the vendor or a coordinator was informed, total time to patch at discovery, and disclosure to patch at public disclosure; vendor response time runs from the report to its acknowledgement. Time to exploit and time unpatched start at the earliest discovery or report, falling back to public disclosure. Unpatched time ends at the first recorded patch, or the calculation time when no patch is recorded. Exploitation to patch shows the interval between those two events; a published proof of concept is a public exploit, not exploitation.
Each result shows its source dates. A negative interval means the end event came first; when date-only inputs leave the order open, the result says so. Date-only inputs are approximate. The earliest evidence wins: KEV report dates and sightings are labelled as such. Records describing another vulnerability are listed but never calculated from, and a PoC alone does not establish exploitation. Missing patch evidence does not prove that no patch exists. Filters below change the event list only.
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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.