{"dataType":"CVE_RECORD","dataVersion":"5.2","cveMetadata":{"cveId":"CVE-2026-89635","assignerOrgId":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","state":"PUBLISHED","assignerShortName":"Linux","dateReserved":"2026-09-11T19:38:34.739Z","datePublished":"2026-09-11T19:45:29.551Z","dateUpdated":"2026-09-13T06:32:14.676Z"},"containers":{"cna":{"providerMetadata":{"orgId":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","shortName":"Linux","dateUpdated":"2026-09-13T06:32:14.676Z"},"descriptions":[{"lang":"en","value":"In the Linux kernel, the following vulnerability has been resolved:\n\nksmbd: only rebind the reopened file's own oplock on durable reconnect\n\nksmbd_reopen_durable_fd() walks the inode's m_op_list and rebinds every\ndetached oplock to the reconnecting session:\n\n\tlist_for_each_entry_rcu(op, &ci->m_op_list, op_entry,\n\t\t\t\tlockdep_is_held(&ci->m_lock)) {\n\t\tif (op->conn)\n\t\t\tcontinue;\n\t\top->conn = ksmbd_conn_get(fp->conn);\n\t\top->sess = work->sess;\n\t}\n\nThe only key is op->conn == NULL, which every detached durable handle on\nthat inode matches, not just the one owned by fp.  When two sessions hold\ndurable handles on the same file and both disconnect, reconnecting one of\nthem adopts the other session's oplock: op->sess is overwritten with the\nreconnecting session without taking a reference on it, while op->conn\npins the connection.\n\nThe sibling teardown path, session_fd_check(), keys on the identity of\nthe connection being torn down (op->conn == conn) rather than on shared\nstate, and so does not have this problem.\n\nOnce the adopting session is destroyed, ksmbd_session_destroy() frees it\nwhile the foreign oplock still points at it.  The reader in\nksmbd_close_fd_app_instance_id() validates only opinfo->conn, which is\nstill live thanks to the reference taken above, and then dereferences the\nstale session:\n\n\tif (!opinfo->conn) {\n\t\tup_read(&fp->f_ci->m_lock);\n\t\tgoto out;\n\t}\n\n\tft = &opinfo->sess->file_table;\n\twrite_lock(&ft->lock);\n\n  BUG: KASAN: slab-use-after-free in _raw_write_lock+0x74/0xd0\n  Write of size 4 at addr ffff88810a970528 by task kworker/0:0/9\n  Workqueue: ksmbd-io handle_ksmbd_work\n  Call Trace:\n   _raw_write_lock+0x74/0xd0\n   ksmbd_close_fd_app_instance_id+0x183/0x410\n   smb2_open+0x1346/0x4430\n   handle_ksmbd_work+0x2bb/0x7b0\n\nReached from an authenticated session against a share with the default\ndurable-handle and oplock configuration: two sessions open the same file\nwith a durable-v2 handle and an RH lease under distinct AppInstanceIds,\nboth log off, one reconnects with DH2C, and a later durable-v2 create\ncarrying the other AppInstanceId walks into the freed session.\n\nConstrain the loop to the oplock owned by the file being reopened."}],"metrics":[{"cvssV3_1":{"version":"3.1","vectorString":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H","baseScore":9.8,"baseSeverity":"CRITICAL"},"scenarios":[{"lang":"en","value":"AV:N - ksmbd is the in-kernel SMB server on TCP/445; the UAF is reached from remote SMB2 CREATE (DH2C durable reconnect, then a later AppInstanceId create) via ksmbd_conn_handler_loop() through handle_ksmbd_work(), smb2_open(), ksmbd_reopen_durable_fd(), and ksmbd_close_fd_app_instance_id().\nAC:L - The attacker fully drives both sessions: open the same file with durable-v2 RH leases and distinct AppInstanceIds, log off both, reconnect one with DH2C (misbinding the sibling oplock), destroy that session, then CREATE with the other AppInstanceId. No victim-dependent race, heap layout, or rare kernel config is required.\nPR:N - SMB2 CREATE needs a session and tree connect, but ksmbd supports guest/anonymous users and guest shares; guest session setup skips NTLMSSP password verification, so a reasonable NAS/IoT deployment lets an unauthenticated network client reach this path without a named account.\nUI:N - No victim action is required; the attacker programmatically issues SESSION_SETUP, TREE_CONNECT, CREATE, LOGOFF, DH2C reconnect, and the follow-up AppInstanceId CREATE on their own SMB connections.\nS:U - The UAF corrupts ksmbd/kernel heap on the SMB server host and can escalate privileges within that kernel; it does not cross a VM, guest-to-host, container, or IOMMU/DMA security boundary.\nC:H - Use-after-free of a ksmbd_session object: after the adopted session is kfree'd in ksmbd_session_destroy(), ksmbd_close_fd_app_instance_id() still sees a live opinfo->conn and dereferences the stale opinfo->sess, enabling arbitrary kernel disclosure via heap reuse.\nI:H - The UAF takes write_lock on the freed session's file_table.lock (KASAN 4-byte write) and may idr_remove through the stale table; with heap spray this yields arbitrary kernel writes and control-flow hijacking, matching High integrity for session-object UAF.\nA:H - KASAN reports slab-use-after-free in _raw_write_lock from ksmbd_close_fd_app_instance_id during smb2_open on ksmbd-io; the dangling session pointer causes kernel oops or panic on worker threads and is repeatable by resending the CREATE sequence."}]}],"affected":[{"product":"Linux","vendor":"Linux","defaultStatus":"unaffected","repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["fs/smb/server/vfs_cache.c"],"versions":[{"version":"f363a0fb134a3eb9e47368b1edbd251fd76be84b","lessThan":"74e3ef4630f004c0de40c0540648a5a4033c6c9d","status":"affected","versionType":"git"},{"version":"f363a0fb134a3eb9e47368b1edbd251fd76be84b","lessThan":"3f220a0a62e6b9b391c9d1f0e6580b05173cc7f7","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/server/vfs_cache.c"],"versions":[{"version":"7.2","status":"affected"},{"version":"0","lessThan":"7.2","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":"7.2","versionEndExcluding":"7.2.4"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"7.2","versionEndExcluding":"7.3-rc1"}]}]}],"references":[{"url":"https://git.kernel.org/stable/c/74e3ef4630f004c0de40c0540648a5a4033c6c9d"},{"url":"https://git.kernel.org/stable/c/3f220a0a62e6b9b391c9d1f0e6580b05173cc7f7"}],"title":"ksmbd: only rebind the reopened file's own oplock on durable reconnect","x_generator":{"engine":"bippy-1.2.0"}}}}