CVE-2026-64298 (GCVE-0-2026-64298)
Vulnerability from cvelistv5 – Published: 2026-07-25 08:49 – Updated: 2026-07-27 04:59
VLAI
EPSS
VEX
Title
NFSv4: include MAY_WRITE in open permission mask for O_TRUNC
Summary
In the Linux kernel, the following vulnerability has been resolved:
NFSv4: include MAY_WRITE in open permission mask for O_TRUNC
POSIX requires write permission to truncate a file, so an open() that
specifies O_TRUNC must be authorized for write access regardless of the
O_ACCMODE access mode.
nfs_open_permission_mask() builds the access mask passed to
nfs_may_open(), which is the local authorization gate for OPENs the
client serves itself from a cached write delegation via the
can_open_delegated() path in nfs4_try_open_cached(). The mask is
derived from O_ACCMODE alone, so an open(O_RDONLY | O_TRUNC) against a
file the caller cannot write requests only MAY_READ and passes the
local check. The OPEN is then satisfied locally and the truncation is
issued to the server as a SETATTR(size=0) over the delegation stateid,
which the server accepts under standard write-delegation semantics.
POSIX requires that this open fail with EACCES.
Include MAY_WRITE in the mask whenever O_TRUNC is set so the local
check matches the access the server would have enforced.
Severity
7.1 (High)
Assigner
References
8 references
Impacted products
2 products
| Vendor | Product | Version | |
|---|---|---|---|
| Linux | Linux |
Affected:
af22f94ae02ab9dd4fd7fe628c8434a59cc293be , < 4817c8974315b666e895b7d1bb83cd3664c323b1
(git)
Affected: af22f94ae02ab9dd4fd7fe628c8434a59cc293be , < cb148a2762d644bff1894728e8835a9a4b84f9ea (git) Affected: af22f94ae02ab9dd4fd7fe628c8434a59cc293be , < 30fdf4df6c3c00efec947e4ddf97f0fdd4473628 (git) Affected: af22f94ae02ab9dd4fd7fe628c8434a59cc293be , < 22c1fd1355ad4ca27aa7f0fa02719122dd92d9de (git) Affected: af22f94ae02ab9dd4fd7fe628c8434a59cc293be , < 6bd7d0a06b53c4e797e1a9cea0d2d41aa1b26230 (git) Affected: af22f94ae02ab9dd4fd7fe628c8434a59cc293be , < a937e92c1d00534b5c2e3e9f4381b7e988180797 (git) Affected: af22f94ae02ab9dd4fd7fe628c8434a59cc293be , < e36501b7d4abdcd6d69a7cb901b2f286b7a3d041 (git) Affected: af22f94ae02ab9dd4fd7fe628c8434a59cc293be , < 5140f099ecd8a2f2808b7f7b720ee1bad8468974 (git) |
|
| Linux | Linux |
Affected:
2.6.24
Unaffected: 0 , < 2.6.24 (semver) Unaffected: 5.10.261 , ≤ 5.10.* (semver) Unaffected: 5.15.212 , ≤ 5.15.* (semver) Unaffected: 6.1.178 , ≤ 6.1.* (semver) Unaffected: 6.6.145 , ≤ 6.6.* (semver) Unaffected: 6.12.96 , ≤ 6.12.* (semver) Unaffected: 6.18.39 , ≤ 6.18.* (semver) Unaffected: 7.1.4 , ≤ 7.1.* (semver) Unaffected: 7.2-rc3 , ≤ * (original_commit_for_fix) |
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"value": "In the Linux kernel, the following vulnerability has been resolved:\n\nNFSv4: include MAY_WRITE in open permission mask for O_TRUNC\n\nPOSIX requires write permission to truncate a file, so an open() that\nspecifies O_TRUNC must be authorized for write access regardless of the\nO_ACCMODE access mode.\n\nnfs_open_permission_mask() builds the access mask passed to\nnfs_may_open(), which is the local authorization gate for OPENs the\nclient serves itself from a cached write delegation via the\ncan_open_delegated() path in nfs4_try_open_cached(). The mask is\nderived from O_ACCMODE alone, so an open(O_RDONLY | O_TRUNC) against a\nfile the caller cannot write requests only MAY_READ and passes the\nlocal check. The OPEN is then satisfied locally and the truncation is\nissued to the server as a SETATTR(size=0) over the delegation stateid,\nwhich the server accepts under standard write-delegation semantics.\nPOSIX requires that this open fail with EACCES.\n\nInclude MAY_WRITE in the mask whenever O_TRUNC is set so the local\ncheck matches the access the server would have enforced."
}
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"url": "https://git.kernel.org/stable/c/5140f099ecd8a2f2808b7f7b720ee1bad8468974"
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"datePublished": "2026-07-25T08:49:35.101Z",
"dateReserved": "2026-07-19T15:36:31.778Z",
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"date": "2026-07-26",
"epss": "0.00211",
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"product_status:under_investigation": "1",
"source": "Microsoft CSAF VEX",
"status": "final",
"title": "NFSv4: include MAY_WRITE in open permission mask for O_TRUNC",
"url": "https://msrc.microsoft.com/csaf/vex/2026/msrc_cve-2026-64298.json",
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"suse_vex": {
"aggregate_severity": "not set",
"current_release_date": "2026-07-25T16:46:17Z",
"cve": "CVE-2026-64298",
"id": "CVE-2026-64298",
"initial_release_date": "2026-07-25T16:46:17Z",
"source": "SUSE CSAF VEX",
"status": "interim",
"title": "SUSE CVE CVE-2026-64298",
"url": "https://ftp.suse.com/pub/projects/security/csaf-vex/cve-2026-64298.json",
"version": "2"
}
}
}
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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.
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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.
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