{"id":"CVE-2026-89637","revision":"275d5407de204d2a90b1bdf511318839","records":[{"revision":"275d5407de204d2a90b1bdf511318839","observedAt":"2026-10-23T15:48:27.903+00:00","statement":{"source":"cve-program","id":"CVE-2026-89637","aliases":[],"title":"smb: client: fix UAF and buffer leak in cifs_check_trans2() for malformed secondary T2","description":"In the Linux kernel, the following vulnerability has been resolved:\n\nsmb: client: fix UAF and buffer leak in cifs_check_trans2() for malformed secondary T2\n\nWhen a valid primary TRANSACT2 response has been received (mid->resp_buf\nset, mid->multiRsp true) and a subsequent secondary response causes\ncifs_check_trans2() to return false -- either because the SMB header is\ninvalid (malformed != 0) or because check2ndT2() rejects the PDU --\nhandle_mid() overwrites mid->resp_buf with the new buffer (leaking the\nprimary buffer) and, because mid->multiRsp is set, skips the\nserver->smallbuf/bigbuf NULL-out.  When the user thread frees\nmid->resp_buf, server->smallbuf or server->bigbuf is left dangling; the\ndemux thread reuses it for the next packet, resulting in a use-after-free.\n\nCombine both early-exit conditions and, when mid->multiRsp is already\nset, abort the pending transaction inline: set multiEnd, call\ndequeue_mid() with malformed=true, and return true so handle_mid() exits\nwithout touching mid->resp_buf or the server buffer pointers.","state":0,"publishedAt":"2026-09-11T19:45:31.048+00:00","modifiedAt":"2026-10-19T08:50:09.23+00:00","affected":[{"ecosystem":"Vendor product","name":"Linux","ranges":[],"versions":[],"rawVersionEvidence":"{\n                    \"product\": \"Linux\",\n                    \"vendor\": \"Linux\",\n                    \"defaultStatus\": \"unaffected\",\n                    \"repo\": \"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git\",\n                    \"programFiles\": [\n                        \"fs/smb/client/smb1transport.c\"\n                    ],\n                    \"versions\": [\n                        {\n                            \"version\": \"316cf94a910f6f93d43cc574359d163ccae098a3\",\n                            \"lessThan\": \"9eed72e9534b10a6d9f8f5146feff3db53aebdba\",\n                            \"status\": \"affected\",\n                            \"versionType\": \"git\"\n                        },\n                        {\n                            \"version\": \"316cf94a910f6f93d43cc574359d163ccae098a3\",\n                            \"lessThan\": \"5e6533a683f6a851158d9f33fb4ea8f4f25d7f84\",\n                            \"status\": \"affected\",\n                            \"versionType\": \"git\"\n                        },\n                        {\n                            \"version\": \"316cf94a910f6f93d43cc574359d163ccae098a3\",\n                            \"lessThan\": \"730d0bb19507b9e19c2fe5343109ac618e2fbce5\",\n                            \"status\": \"affected\",\n                            \"versionType\": \"git\"\n                        }\n                    ]\n                }"},{"ecosystem":"Vendor product","name":"Linux","ranges":[],"versions":[],"rawVersionEvidence":"{\n                    \"product\": \"Linux\",\n                    \"vendor\": \"Linux\",\n                    \"defaultStatus\": \"affected\",\n                    \"repo\": \"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git\",\n                    \"programFiles\": [\n                        \"fs/smb/client/smb1transport.c\"\n                    ],\n                    \"versions\": [\n                        {\n                            \"version\": \"3.6\",\n                            \"status\": \"affected\"\n                        },\n                        {\n                            \"version\": \"0\",\n                            \"lessThan\": \"3.6\",\n                            \"status\": \"unaffected\",\n                            \"versionType\": \"semver\"\n                        },\n                        {\n                            \"version\": \"6.18.51\",\n                            \"lessThanOrEqual\": \"6.18.*\",\n                            \"status\": \"unaffected\",\n                            \"versionType\": \"semver\"\n                        },\n                        {\n                            \"version\": \"7.2.4\",\n                            \"lessThanOrEqual\": \"7.2.*\",\n                            \"status\": \"unaffected\",\n                            \"versionType\": \"semver\"\n                        },\n                        {\n                            \"version\": \"7.3\",\n                            \"lessThanOrEqual\": \"*\",\n                            \"status\": \"unaffected\",\n                            \"versionType\": \"original_commit_for_fix\"\n                        }\n                    ]\n                }"}],"metrics":[{"system":"CVSS 3.1","vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H","score":9.8,"severity":"CRITICAL"}],"references":["https://git.kernel.org/stable/c/9eed72e9534b10a6d9f8f5146feff3db53aebdba","https://git.kernel.org/stable/c/5e6533a683f6a851158d9f33fb4ea8f4f25d7f84","https://git.kernel.org/stable/c/730d0bb19507b9e19c2fe5343109ac618e2fbce5"],"sourceUrl":"https://www.cve.org/CVERecord?id=CVE-2026-89637","license":"CVE Program Terms of Use","key":"cve-program:CVE-2026-89637","identifiers":["CVE-2026-89637"]},"retained":false,"historicalAffected":[]}],"coverage":[]}