{ "dataType": "CVE_RECORD", "dataVersion": "5.2", "cveMetadata": { "cveId": "CVE-2026-64298", "assignerOrgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "state": "PUBLISHED", "assignerShortName": "Linux", "dateReserved": "2026-07-19T15:36:31.778Z", "datePublished": "2026-07-25T08:49:35.101Z", "dateUpdated": "2026-08-17T04:52:55.989Z" }, "containers": { "cna": { "providerMetadata": { "orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "shortName": "Linux", "dateUpdated": "2026-08-17T04:52:55.989Z" }, "descriptions": [ { "lang": "en", "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." } ], "metrics": [ { "cvssV3_1": { "version": "3.1", "vectorString": "CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:H/A:H", "baseScore": 7.1, "baseSeverity": "HIGH" }, "scenarios": [ { "lang": "en", "value": "AV:L - An unprivileged local process triggers the flaw through open/openat with O_RDONLY|O_TRUNC on an accessible NFSv4-mounted file. The resulting NFS RPC is outbound and does not make the attack remotely reachable.\nAC:L - Once the client holds a standard cached write delegation, a single deterministic open triggers the unauthorized truncation without a race or timing requirement. Delegations persist and the attacker can repeatedly target files actively written through the same client.\nPR:L - The attacker needs only ordinary local access and read/search permission for the target path; no capability or administrative privilege is required. User namespaces are unnecessary.\nUI:N - The attacker invokes open directly and no contemporaneous action by another user is required.\nS:U - The faulty client-side permission check and modification of the delegated NFS file remain within the NFS filesystem access-control authority.\nC:N - The flaw discloses no kernel or file data beyond content the caller was already authorized to read, and it involves no memory corruption.\nI:H - The attacker can irreversibly truncate the complete contents of a file for which write access was denied, causing total integrity loss of that resource.\nA:H - Truncating critical NFS-hosted executables, configuration, databases, or operational data can completely disable dependent systems or services, and the attack can be repeated against additional delegated files." } ] } ], "affected": [ { "product": "Linux", "vendor": "Linux", "defaultStatus": "unaffected", "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git", "programFiles": [ "fs/nfs/dir.c" ], "versions": [ { "version": "af22f94ae02ab9dd4fd7fe628c8434a59cc293be", "lessThan": "4817c8974315b666e895b7d1bb83cd3664c323b1", "status": "affected", "versionType": "git" }, { "version": "af22f94ae02ab9dd4fd7fe628c8434a59cc293be", "lessThan": "cb148a2762d644bff1894728e8835a9a4b84f9ea", "status": "affected", "versionType": "git" }, { "version": "af22f94ae02ab9dd4fd7fe628c8434a59cc293be", "lessThan": "30fdf4df6c3c00efec947e4ddf97f0fdd4473628", "status": "affected", "versionType": "git" }, { "version": "af22f94ae02ab9dd4fd7fe628c8434a59cc293be", "lessThan": "22c1fd1355ad4ca27aa7f0fa02719122dd92d9de", "status": "affected", "versionType": "git" }, { "version": "af22f94ae02ab9dd4fd7fe628c8434a59cc293be", "lessThan": "6bd7d0a06b53c4e797e1a9cea0d2d41aa1b26230", "status": "affected", "versionType": "git" }, { "version": "af22f94ae02ab9dd4fd7fe628c8434a59cc293be", "lessThan": "a937e92c1d00534b5c2e3e9f4381b7e988180797", "status": "affected", "versionType": "git" }, { "version": "af22f94ae02ab9dd4fd7fe628c8434a59cc293be", "lessThan": "e36501b7d4abdcd6d69a7cb901b2f286b7a3d041", "status": "affected", "versionType": "git" }, { "version": "af22f94ae02ab9dd4fd7fe628c8434a59cc293be", "lessThan": "5140f099ecd8a2f2808b7f7b720ee1bad8468974", "status": "affected", "versionType": "git" } ] }, { "product": "Linux", "vendor": "Linux", "defaultStatus": "affected", "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git", "programFiles": [ "fs/nfs/dir.c" ], "versions": [ { "version": "2.6.24", "status": "affected" }, { "version": "0", "lessThan": "2.6.24", "status": "unaffected", "versionType": "semver" }, { "version": "5.10.261", "lessThanOrEqual": "5.10.*", "status": "unaffected", "versionType": "semver" }, { "version": "5.15.212", "lessThanOrEqual": "5.15.*", "status": "unaffected", "versionType": "semver" }, { "version": "6.1.178", "lessThanOrEqual": "6.1.*", "status": "unaffected", "versionType": "semver" }, { "version": "6.6.145", "lessThanOrEqual": "6.6.*", "status": "unaffected", "versionType": "semver" }, { "version": "6.12.96", "lessThanOrEqual": "6.12.*", "status": "unaffected", "versionType": "semver" }, { "version": "6.18.39", "lessThanOrEqual": "6.18.*", "status": "unaffected", "versionType": "semver" }, { "version": "7.1.4", "lessThanOrEqual": "7.1.*", "status": "unaffected", "versionType": "semver" }, { "version": "7.2", "lessThanOrEqual": "*", "status": "unaffected", "versionType": "original_commit_for_fix" } ] } ], "cpeApplicability": [ { "nodes": [ { "operator": "OR", "negate": false, "cpeMatch": [ { "vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "2.6.24", "versionEndExcluding": "5.10.261" }, { "vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "2.6.24", "versionEndExcluding": "5.15.212" }, { "vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "2.6.24", "versionEndExcluding": "6.1.178" }, { "vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "2.6.24", "versionEndExcluding": "6.6.145" }, { "vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "2.6.24", "versionEndExcluding": "6.12.96" }, { "vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "2.6.24", "versionEndExcluding": "6.18.39" }, { "vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "2.6.24", "versionEndExcluding": "7.1.4" }, { "vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "2.6.24", "versionEndExcluding": "7.2" } ] } ] } ], "references": [ { "url": "https://git.kernel.org/stable/c/4817c8974315b666e895b7d1bb83cd3664c323b1" }, { "url": "https://git.kernel.org/stable/c/cb148a2762d644bff1894728e8835a9a4b84f9ea" }, { "url": "https://git.kernel.org/stable/c/30fdf4df6c3c00efec947e4ddf97f0fdd4473628" }, { "url": "https://git.kernel.org/stable/c/22c1fd1355ad4ca27aa7f0fa02719122dd92d9de" }, { "url": "https://git.kernel.org/stable/c/6bd7d0a06b53c4e797e1a9cea0d2d41aa1b26230" }, { "url": "https://git.kernel.org/stable/c/a937e92c1d00534b5c2e3e9f4381b7e988180797" }, { "url": "https://git.kernel.org/stable/c/e36501b7d4abdcd6d69a7cb901b2f286b7a3d041" }, { "url": "https://git.kernel.org/stable/c/5140f099ecd8a2f2808b7f7b720ee1bad8468974" } ], "title": "NFSv4: include MAY_WRITE in open permission mask for O_TRUNC", "x_generator": { "engine": "bippy-1.2.0" } } } }