{"id":"CVE-2026-31610","summary":"ksmbd: fix mechToken leak when SPNEGO decode fails after token alloc","details":"In the Linux kernel, the following vulnerability has been resolved:\n\nksmbd: fix mechToken leak when SPNEGO decode fails after token alloc\n\nThe kernel ASN.1 BER decoder calls action callbacks incrementally as it\nwalks the input.  When ksmbd_decode_negTokenInit() reaches the mechToken\n[2] OCTET STRING element, ksmbd_neg_token_alloc() allocates\nconn-\u003emechToken immediately via kmemdup_nul().  If a later element in\nthe same blob is malformed, then the decoder will return nonzero after\nthe allocation is already live.  This could happen if mechListMIC [3]\noverrunse the enclosing SEQUENCE.\n\ndecode_negotiation_token() then sets conn-\u003euse_spnego = false because\nboth the negTokenInit and negTokenTarg grammars failed.  The cleanup at\nthe bottom of smb2_sess_setup() is gated on use_spnego:\n\n\tif (conn-\u003euse_spnego && conn-\u003emechToken) {\n\t\tkfree(conn-\u003emechToken);\n\t\tconn-\u003emechToken = NULL;\n\t}\n\nso the kfree is skipped, causing the mechToken to never be freed.\n\nThis codepath is reachable pre-authentication, so untrusted clients can\ncause slow memory leaks on a server without even being properly\nauthenticated.\n\nFix this up by not checking check for use_spnego, as it's not required,\nso the memory will always be properly freed.  At the same time, always\nfree the memory in ksmbd_conn_free() incase some other failure path\nforgot to free it.","modified":"2026-06-18T03:55:06.238581629Z","published":"2026-04-24T14:42:31.471Z","related":["CGA-h73m-8f9g-xx2h","openSUSE-SU-2026:10703-1"],"database_specific":{"cna_assigner":"Linux","osv_generated_from":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/31xxx/CVE-2026-31610.json"},"references":[{"type":"WEB","url":"https://git.kernel.org/stable/c/269c800a7a7e363459291885b35f7bc72e231ed6"},{"type":"WEB","url":"https://git.kernel.org/stable/c/6c8c44e6553b9f072f62d9875e567766eb293162"},{"type":"WEB","url":"https://git.kernel.org/stable/c/745a535461bbb90a56d9357573c9f97a5c12abe1"},{"type":"WEB","url":"https://git.kernel.org/stable/c/ad0057fb91218914d6c98268718ceb9d59b388e1"},{"type":"WEB","url":"https://git.kernel.org/stable/c/dd53414e301beb915fe672dc4c4a51bafb917604"},{"type":"WEB","url":"https://git.kernel.org/stable/c/dd577cb55588ec3fbc66af3621280306601c4192"},{"type":"ADVISORY","url":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/31xxx/CVE-2026-31610.json"},{"type":"ADVISORY","url":"https://nvd.nist.gov/vuln/detail/CVE-2026-31610"},{"type":"PACKAGE","url":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git"}],"affected":[{"ranges":[{"type":"GIT","repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","events":[{"introduced":"fad4161b5cd01a24202234976ebbb133f7adc0b5"},{"fixed":"745a535461bbb90a56d9357573c9f97a5c12abe1"},{"fixed":"dd577cb55588ec3fbc66af3621280306601c4192"},{"fixed":"dd53414e301beb915fe672dc4c4a51bafb917604"},{"fixed":"269c800a7a7e363459291885b35f7bc72e231ed6"},{"fixed":"6c8c44e6553b9f072f62d9875e567766eb293162"},{"fixed":"ad0057fb91218914d6c98268718ceb9d59b388e1"}]}],"database_specific":{"source":"https://storage.googleapis.com/osv-test-cve-osv-conversion/osv-output/CVE-2026-31610.json"}},{"package":{"name":"Kernel","ecosystem":"Linux"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"5.15.0"},{"fixed":"6.6.136"}]},{"type":"ECOSYSTEM","events":[{"introduced":"6.7.0"},{"fixed":"6.12.83"}]},{"type":"ECOSYSTEM","events":[{"introduced":"6.13.0"},{"fixed":"6.18.24"}]},{"type":"ECOSYSTEM","events":[{"introduced":"6.19.0"},{"fixed":"6.19.14"}]},{"type":"ECOSYSTEM","events":[{"introduced":"6.20.0"},{"fixed":"7.0.1"}]}],"database_specific":{"source":"https://storage.googleapis.com/osv-test-cve-osv-conversion/osv-output/CVE-2026-31610.json"}}],"schema_version":"1.7.5"}