{"id":"CVE-2026-64298","state":"PUBLISHED","title":"NFSv4: include MAY_WRITE in open permission mask for O_TRUNC","description":"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.","publishedAt":"2026-07-25T08:49:35.101Z","updatedAt":"2026-10-19T20:38:22.558Z","severity":{"score":7.1,"label":"High","version":"3.1","vector":"CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:H/A:H","source":"Linux"},"assigner":"Linux","products":["Linux Linux"],"affected":[{"vendor":"Linux","product":"Linux","defaultStatus":"unaffected","versions":[{"version":"af22f94ae02ab9dd4fd7fe628c8434a59cc293be","status":"affected","lessThan":"4817c8974315b666e895b7d1bb83cd3664c323b1","versionType":"git"},{"version":"af22f94ae02ab9dd4fd7fe628c8434a59cc293be","status":"affected","lessThan":"cb148a2762d644bff1894728e8835a9a4b84f9ea","versionType":"git"},{"version":"af22f94ae02ab9dd4fd7fe628c8434a59cc293be","status":"affected","lessThan":"30fdf4df6c3c00efec947e4ddf97f0fdd4473628","versionType":"git"},{"version":"af22f94ae02ab9dd4fd7fe628c8434a59cc293be","status":"affected","lessThan":"22c1fd1355ad4ca27aa7f0fa02719122dd92d9de","versionType":"git"},{"version":"af22f94ae02ab9dd4fd7fe628c8434a59cc293be","status":"affected","lessThan":"6bd7d0a06b53c4e797e1a9cea0d2d41aa1b26230","versionType":"git"},{"version":"af22f94ae02ab9dd4fd7fe628c8434a59cc293be","status":"affected","lessThan":"a937e92c1d00534b5c2e3e9f4381b7e988180797","versionType":"git"},{"version":"af22f94ae02ab9dd4fd7fe628c8434a59cc293be","status":"affected","lessThan":"e36501b7d4abdcd6d69a7cb901b2f286b7a3d041","versionType":"git"},{"version":"af22f94ae02ab9dd4fd7fe628c8434a59cc293be","status":"affected","lessThan":"5140f099ecd8a2f2808b7f7b720ee1bad8468974","versionType":"git"}],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["fs/nfs/dir.c"]},{"vendor":"Linux","product":"Linux","defaultStatus":"affected","versions":[{"version":"2.6.24","status":"affected"},{"version":"0","status":"unaffected","lessThan":"2.6.24","versionType":"semver"},{"version":"5.10.261","status":"unaffected","lessThanOrEqual":"5.10.*","versionType":"semver"},{"version":"5.15.212","status":"unaffected","lessThanOrEqual":"5.15.*","versionType":"semver"},{"version":"6.1.178","status":"unaffected","lessThanOrEqual":"6.1.*","versionType":"semver"},{"version":"6.6.145","status":"unaffected","lessThanOrEqual":"6.6.*","versionType":"semver"},{"version":"6.12.96","status":"unaffected","lessThanOrEqual":"6.12.*","versionType":"semver"},{"version":"6.18.39","status":"unaffected","lessThanOrEqual":"6.18.*","versionType":"semver"},{"version":"7.1.4","status":"unaffected","lessThanOrEqual":"7.1.*","versionType":"semver"},{"version":"7.2","status":"unaffected","lessThanOrEqual":"*","versionType":"original_commit_for_fix"}],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["fs/nfs/dir.c"]}],"references":["https://git.kernel.org/stable/c/4817c8974315b666e895b7d1bb83cd3664c323b1","https://git.kernel.org/stable/c/cb148a2762d644bff1894728e8835a9a4b84f9ea","https://git.kernel.org/stable/c/30fdf4df6c3c00efec947e4ddf97f0fdd4473628","https://git.kernel.org/stable/c/22c1fd1355ad4ca27aa7f0fa02719122dd92d9de","https://git.kernel.org/stable/c/6bd7d0a06b53c4e797e1a9cea0d2d41aa1b26230","https://git.kernel.org/stable/c/a937e92c1d00534b5c2e3e9f4381b7e988180797","https://git.kernel.org/stable/c/e36501b7d4abdcd6d69a7cb901b2f286b7a3d041","https://git.kernel.org/stable/c/5140f099ecd8a2f2808b7f7b720ee1bad8468974"],"weaknesses":["CWE-862"],"ingestedAt":"2026-10-29T20:12:41.951Z","source":{"repository":"CVEProject/cvelistV5","path":"cves/2026/64xxx/CVE-2026-64298.json","commit":"556c9d3a8cd17e218bb8e452ba7cd619a384ff47"},"raw":{"dataType":"CVE_RECORD","dataVersion":"5.2","cveMetadata":{"cveId":"CVE-2026-64298","state":"PUBLISHED","datePublished":"2026-07-25T08:49:35.101Z","dateUpdated":"2026-10-19T20:38:22.558Z","assignerShortName":"Linux","assignerOrgId":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","dateReserved":"2026-07-19T15:36:31.778Z"},"containers":{"cna":{"title":"NFSv4: include MAY_WRITE in open permission mask for O_TRUNC","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."}],"affected":[{"vendor":"Linux","product":"Linux","defaultStatus":"unaffected","versions":[{"version":"af22f94ae02ab9dd4fd7fe628c8434a59cc293be","status":"affected","lessThan":"4817c8974315b666e895b7d1bb83cd3664c323b1","versionType":"git"},{"version":"af22f94ae02ab9dd4fd7fe628c8434a59cc293be","status":"affected","lessThan":"cb148a2762d644bff1894728e8835a9a4b84f9ea","versionType":"git"},{"version":"af22f94ae02ab9dd4fd7fe628c8434a59cc293be","status":"affected","lessThan":"30fdf4df6c3c00efec947e4ddf97f0fdd4473628","versionType":"git"},{"version":"af22f94ae02ab9dd4fd7fe628c8434a59cc293be","status":"affected","lessThan":"22c1fd1355ad4ca27aa7f0fa02719122dd92d9de","versionType":"git"},{"version":"af22f94ae02ab9dd4fd7fe628c8434a59cc293be","status":"affected","lessThan":"6bd7d0a06b53c4e797e1a9cea0d2d41aa1b26230","versionType":"git"},{"version":"af22f94ae02ab9dd4fd7fe628c8434a59cc293be","status":"affected","lessThan":"a937e92c1d00534b5c2e3e9f4381b7e988180797","versionType":"git"},{"version":"af22f94ae02ab9dd4fd7fe628c8434a59cc293be","status":"affected","lessThan":"e36501b7d4abdcd6d69a7cb901b2f286b7a3d041","versionType":"git"},{"version":"af22f94ae02ab9dd4fd7fe628c8434a59cc293be","status":"affected","lessThan":"5140f099ecd8a2f2808b7f7b720ee1bad8468974","versionType":"git"}],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["fs/nfs/dir.c"]},{"vendor":"Linux","product":"Linux","defaultStatus":"affected","versions":[{"version":"2.6.24","status":"affected"},{"version":"0","status":"unaffected","lessThan":"2.6.24","versionType":"semver"},{"version":"5.10.261","status":"unaffected","lessThanOrEqual":"5.10.*","versionType":"semver"},{"version":"5.15.212","status":"unaffected","lessThanOrEqual":"5.15.*","versionType":"semver"},{"version":"6.1.178","status":"unaffected","lessThanOrEqual":"6.1.*","versionType":"semver"},{"version":"6.6.145","status":"unaffected","lessThanOrEqual":"6.6.*","versionType":"semver"},{"version":"6.12.96","status":"unaffected","lessThanOrEqual":"6.12.*","versionType":"semver"},{"version":"6.18.39","status":"unaffected","lessThanOrEqual":"6.18.*","versionType":"semver"},{"version":"7.1.4","status":"unaffected","lessThanOrEqual":"7.1.*","versionType":"semver"},{"version":"7.2","status":"unaffected","lessThanOrEqual":"*","versionType":"original_commit_for_fix"}],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["fs/nfs/dir.c"]}],"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"}],"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."}]}],"providerMetadata":{"shortName":"Linux","orgId":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","dateUpdated":"2026-08-17T04:52:55.989Z"},"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"}]}]}],"x_generator":{"engine":"bippy-1.2.0"}},"adp":[{"title":"CISA ADP Vulnrichment","metrics":[{"other":{"type":"ssvc","content":{"id":"CVE-2026-64298","role":"CISA Coordinator","options":[{"Exploitation":"none"},{"Automatable":"no"},{"Technical Impact":"partial"}],"version":"2.0.3","timestamp":"2026-10-16T15:38:37.476153Z"}}}],"problemTypes":[{"descriptions":[{"cweId":"CWE-862","lang":"en","type":"CWE","description":"CWE-862 Missing Authorization"}]}],"providerMetadata":{"shortName":"CISA-ADP","orgId":"134c704f-9b21-4f2e-91b3-4a467353bcc0","dateUpdated":"2026-10-19T20:38:22.558Z"}}]}}}