{"dataType":"CVE_RECORD","dataVersion":"5.2","cveMetadata":{"cveId":"CVE-2026-89641","assignerOrgId":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","state":"PUBLISHED","assignerShortName":"Linux","dateReserved":"2026-09-11T19:38:34.740Z","datePublished":"2026-09-11T19:45:34.036Z","dateUpdated":"2026-09-13T06:32:21.616Z"},"containers":{"cna":{"providerMetadata":{"orgId":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","shortName":"Linux","dateUpdated":"2026-09-13T06:32:21.616Z"},"descriptions":[{"lang":"en","value":"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(), 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."}],"metrics":[{"cvssV3_1":{"version":"3.1","vectorString":"CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H","baseScore":7.8,"baseSeverity":"HIGH"},"scenarios":[{"lang":"en","value":"AV:L - The UAF is in the CIFS client setattr path (fs/smb/client/inode.c cifs_file_set_size), reached only via local VFS truncate/setattr on a mounted SMB share (sys_truncate → vfs_truncate → notify_change → cifs_setattr), not via ksmbd or unsolicited SMB receive processing.\nAC:L - A local attacker controls both sides: keep a writable handle open, issue truncate(2) to hit the find_writable_file() else branch, fail handle-based set_file_size (controlled/malicious server or reconnect), and concurrently umount/teardown so TCON_LINK_IN_TREE is already cleared when cifsFileInfo_put() drops the last tlink ref.\nPR:L - Any unprivileged user with write access on an existing CIFS mount can invoke truncate(2); vfs_truncate only requires MAY_WRITE and setattr_prepare does not demand CAP_SYS_ADMIN. CIFS is not FS_USERNS_MOUNT, but the vulnerable path itself needs no init-namespace capability.\nUI:N - The attacker performs open/truncate (and optional umount) themselves on a reachable CIFS mount such as an enterprise automount or a share they mounted; no separate victim action is required at exploit time.\nS:U - This is a standard in-kernel heap use-after-free of struct cifs_tcon on the client host, enabling privilege escalation within the same kernel security authority and not a VM, IOMMU, or sandbox escape.\nC:H - After cifsFileInfo_put() can free tcon, set_path_size()/smb2_compound_op() reads the freed cifs_tcon; kernel UAF of this heap object enables reuse/spraying and arbitrary kernel memory disclosure.\nI:H - The same freed tcon is passed into SMB2 compound operations that write tcon fields and follow tcon->ses pointers, so heap spraying yields arbitrary write and potential control-flow hijack primitives.\nA:H - Use-after-free of tcon in the path-based set_path_size fallback causes kernel oops/panic even without full exploitation, fully denying availability."}]}],"affected":[{"product":"Linux","vendor":"Linux","defaultStatus":"unaffected","repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["fs/smb/client/inode.c"],"versions":[{"version":"110fee6b9bb58a5c50047fc2594d415f741b591e","lessThan":"4f18c9e7ee464aaae5cd9fccdb943b3fcb4655d4","status":"affected","versionType":"git"},{"version":"110fee6b9bb58a5c50047fc2594d415f741b591e","lessThan":"4bea15d9c7683218f57b8c1f5f0aa75cab76af8d","status":"affected","versionType":"git"},{"version":"110fee6b9bb58a5c50047fc2594d415f741b591e","lessThan":"b96db32fed8dfb2478d7c208f89bf383beed1535","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/smb/client/inode.c"],"versions":[{"version":"6.18","status":"affected"},{"version":"0","lessThan":"6.18","status":"unaffected","versionType":"semver"},{"version":"6.18.50","lessThanOrEqual":"6.18.*","status":"unaffected","versionType":"semver"},{"version":"7.2.4","lessThanOrEqual":"7.2.*","status":"unaffected","versionType":"semver"},{"version":"7.3-rc1","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":"6.18","versionEndExcluding":"6.18.50"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"6.18","versionEndExcluding":"7.2.4"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"6.18","versionEndExcluding":"7.3-rc1"}]}]}],"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"}],"title":"cifs: clear tcon after cifsFileInfo_put() in cifs_file_set_size()","x_generator":{"engine":"bippy-1.2.0"}}}}