{"id":"CVE-2026-89641","title":"cifs: clear tcon after cifsFileInfo_put() in cifs_file_set_size()","summary":"In the Linux kernel, the following vulnerability has been resolved:\n\ncifs: clear tcon after cifsFileInfo_put() in cifs_file_set_size()\n\nWhen the else branch of cifs_file_set_size() finds a writable file handle\nvia find_writable_file(), i…","severity":"high","cvss":7.8,"cvssVector":"CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H","cvssSource":"cna","cwe":["CWE-825"],"vendor":"Linux","product":"Linux","affected":["Linux >= 110fee6b9bb58a5c50047fc2594d415f741b591e < 4f18c9e7ee464aaae5cd9fccdb943b3fcb4655d4","Linux >= 110fee6b9bb58a5c50047fc2594d415f741b591e < 4bea15d9c7683218f57b8c1f5f0aa75cab76af8d","Linux >= 110fee6b9bb58a5c50047fc2594d415f741b591e < b96db32fed8dfb2478d7c208f89bf383beed1535","Linux 6.18"],"published":"2026-09-11","updated":"2026-10-19","sourceUpdated":"2026-10-19T08:50:13.143Z","source":"CVEORG","sourceUrl":"https://www.cve.org/CVERecord?id=CVE-2026-89641","references":[{"url":"https://git.kernel.org/stable/c/4f18c9e7ee464aaae5cd9fccdb943b3fcb4655d4"},{"url":"https://git.kernel.org/stable/c/4bea15d9c7683218f57b8c1f5f0aa75cab76af8d"},{"url":"https://git.kernel.org/stable/c/b96db32fed8dfb2478d7c208f89bf383beed1535"},{"url":"https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-89641.json"},{"url":"https://access.redhat.com/security/cve/CVE-2026-89641"},{"url":"https://bugzilla.redhat.com/show_bug.cgi?id=2532505"},{"url":"https://www.cve.org/CVERecord?id=CVE-2026-89641"},{"url":"https://nvd.nist.gov/vuln/detail/CVE-2026-89641"},{"url":"https://git.kernel.org/pub/scm/linux/security/vulns.git/plain/cve/published/2026/CVE-2026-89641.mbox"}],"tags":["cve.org","csaf","vex","red-hat"],"epss":0.0014,"epssPercentile":0.03293,"scores":{"cna":7.8,"vendor":7},"ingestedAt":"2026-09-14T15:23:07.473Z","slug":"CVE-2026-89641","body":"## Overview\n\nIn the Linux kernel, the following vulnerability has been resolved:\n\ncifs: clear tcon after cifsFileInfo_put() in cifs_file_set_size()\n\nWhen the else branch of cifs_file_set_size() finds a writable file handle\nvia find_writable_file(), it borrows tcon and server from the handle's\ntlink, attempts the handle-based set_file_size() RPC, and then releases\nthe handle with cifsFileInfo_put().\n\nIf set_file_size() fails, execution falls through to the path-based\nfallback, which reuses the borrowed tcon and server under the\n\"if (tcon == NULL)\" guard.  Since tcon is not NULL at that point, the\nguard is skipped.  If cifsFileInfo_put() dropped the last reference on a\ntlink that was already removed from the tlink tree (TCON_LINK_IN_TREE\ncleared, as happens during reconnection or session teardown),\ncifs_put_tlink() will have freed tcon; the subsequent set_path_size()\ncall is then a use-after-free.\n\nSetting tcon = NULL after cifsFileInfo_put() causes the existing guard\nto take the cifs_sb_tlink() path, which acquires a fresh reference for\nthe path-based operation or fails cleanly if the session is gone.\n\n## Affected\n\n- `Linux >= 110fee6b9bb58a5c50047fc2594d415f741b591e < 4f18c9e7ee464aaae5cd9fccdb943b3fcb4655d4`\n- `Linux >= 110fee6b9bb58a5c50047fc2594d415f741b591e < 4bea15d9c7683218f57b8c1f5f0aa75cab76af8d`\n- `Linux >= 110fee6b9bb58a5c50047fc2594d415f741b591e < b96db32fed8dfb2478d7c208f89bf383beed1535`\n- `Linux 6.18`\n\n## Remediation\n\nRefer to the linked advisories for vendor-supplied fixes and affected version ranges.\n\n## Vendor advisories\n\n- **Red Hat VEX** · Moderate · affected: Red Hat Enterprise Linux 10, Red Hat Enterprise Linux 9, Red Hat OpenShift Container Platform 4 · no fix planned: Red Hat Enterprise Linux 10, Red Hat Enterprise Linux 9, Red Hat OpenShift Container Platform 4 · updated 2026-09-15 · [vex](https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-89641.json)","depth":"twilight","depthScore":43,"depthScoreParts":{"impact":42.9,"likelihood":0,"exploitation":0,"ransomware":0},"changes":[{"seq":224647,"id":"CVE-2026-89641","ts":1792401457749,"field":"cvss","old":"7","new":"7.8"},{"seq":203942,"id":"CVE-2026-89641","ts":1789490230693,"field":"cvss","old":"4.7","new":"7"},{"seq":203941,"id":"CVE-2026-89641","ts":1789490230693,"field":"severity","old":"medium","new":"high"},{"seq":203005,"id":"CVE-2026-89641","ts":1789403733316,"field":"cvss","old":"7.8","new":"4.7"},{"seq":203004,"id":"CVE-2026-89641","ts":1789403733316,"field":"severity","old":"high","new":"medium"},{"seq":197813,"id":"CVE-2026-89641","ts":1789384320508,"field":"cvss","old":"4.7","new":"7.8"},{"seq":197812,"id":"CVE-2026-89641","ts":1789384320508,"field":"severity","old":"medium","new":"high"},{"seq":183719,"id":"CVE-2026-89641","ts":1789356677092,"field":"cvss","old":"7.8","new":"4.7"},{"seq":183718,"id":"CVE-2026-89641","ts":1789356677092,"field":"severity","old":"high","new":"medium"},{"seq":153486,"id":"CVE-2026-89641","ts":1789285350711,"field":"cvss","old":null,"new":"7.8"},{"seq":153485,"id":"CVE-2026-89641","ts":1789285350711,"field":"severity","old":"none","new":"high"},{"seq":147145,"id":"CVE-2026-89641","ts":1789270196797,"field":"cvss","old":null,"new":"4.7"},{"seq":147144,"id":"CVE-2026-89641","ts":1789270196797,"field":"severity","old":"none","new":"medium"},{"seq":108896,"id":"CVE-2026-89641","ts":1789183729447,"field":"cvss","old":null,"new":"4.7"},{"seq":108895,"id":"CVE-2026-89641","ts":1789183729447,"field":"severity","old":"none","new":"medium"}]}