{"id":"CVE-2026-64298","url":"https://www.cyber-defence.io/tools/cve/CVE-2026-64298","generatedAt":"2026-10-28T04:37:40.736Z","title":"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…","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.","published":"2026-07-25T10:17:11.000Z","lastModified":"2026-10-19T21:17:30.000Z","status":"Modified","sourceIdentifier":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","cvss":{"version":"3.1","score":7.1,"severity":"HIGH","vector":"CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:H/A:H"},"cwe":["CWE-862"],"affected":["linux/linux kernel"],"epss":{"score":0.00147,"percentile":0.03896,"date":"2026-10-27","history":[]},"kev":{"listed":false},"exploits":{"count":0,"verified":false,"firstPublished":null,"source":"Exploit-DB (https://gitlab.com/exploit-database/exploitdb)","entries":[]},"verdict":{"level":"high","text":"High impact if exploited, but EPSS currently rates exploitation as unlikely (0.15%). Schedule it in the normal patch cycle and watch for a rise in EPSS or a public exploit."},"changes":[],"references":[{"url":"https://git.kernel.org/stable/c/22c1fd1355ad4ca27aa7f0fa02719122dd92d9de","tags":["Patch"],"source":"416baaa9-dc9f-4396-8d5f-8c081fb06d67"},{"url":"https://git.kernel.org/stable/c/30fdf4df6c3c00efec947e4ddf97f0fdd4473628","tags":["Patch"],"source":"416baaa9-dc9f-4396-8d5f-8c081fb06d67"},{"url":"https://git.kernel.org/stable/c/4817c8974315b666e895b7d1bb83cd3664c323b1","tags":["Patch"],"source":"416baaa9-dc9f-4396-8d5f-8c081fb06d67"},{"url":"https://git.kernel.org/stable/c/5140f099ecd8a2f2808b7f7b720ee1bad8468974","tags":["Patch"],"source":"416baaa9-dc9f-4396-8d5f-8c081fb06d67"},{"url":"https://git.kernel.org/stable/c/6bd7d0a06b53c4e797e1a9cea0d2d41aa1b26230","tags":["Patch"],"source":"416baaa9-dc9f-4396-8d5f-8c081fb06d67"},{"url":"https://git.kernel.org/stable/c/a937e92c1d00534b5c2e3e9f4381b7e988180797","tags":["Patch"],"source":"416baaa9-dc9f-4396-8d5f-8c081fb06d67"},{"url":"https://git.kernel.org/stable/c/cb148a2762d644bff1894728e8835a9a4b84f9ea","tags":["Patch"],"source":"416baaa9-dc9f-4396-8d5f-8c081fb06d67"},{"url":"https://git.kernel.org/stable/c/e36501b7d4abdcd6d69a7cb901b2f286b7a3d041","tags":["Patch"],"source":"416baaa9-dc9f-4396-8d5f-8c081fb06d67"}],"sources":{"nvd":"https://nvd.nist.gov/vuln/detail/CVE-2026-64298","epss":"https://www.first.org/epss/","kev":"https://www.cisa.gov/known-exploited-vulnerabilities-catalog","exploitdb":"https://www.exploit-db.com/"},"licence":"CC BY 4.0 — link back to the CVE Explorer if you publish the results; upstream data remains subject to its own terms."}