{"id":"CVE-2026-31610","url":"https://www.cyber-defence.io/tools/cve/CVE-2026-31610","generatedAt":"2026-10-28T06:14:22.397Z","title":"In the Linux kernel, the following vulnerability has been resolved: ksmbd: fix mechToken leak when SPNEGO decode fails after token alloc The kernel ASN.1 BER decoder calls action callbacks incrementally as it walks the input.","description":"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->mechToken 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->use_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->use_spnego && conn->mechToken) {\n\t\tkfree(conn->mechToken);\n\t\tconn->mechToken = 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.","published":"2026-04-24T15:16:40.000Z","lastModified":"2026-07-24T15:17:16.000Z","status":"Modified","sourceIdentifier":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","cvss":{"version":"3.1","score":5.5,"severity":"MEDIUM","vector":"CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H"},"cwe":["CWE-401"],"affected":["linux/linux kernel"],"epss":{"score":0.00136,"percentile":0.03017,"date":"2026-10-27","history":[]},"kev":{"listed":false},"exploits":{"count":0,"verified":false,"firstPublished":null,"source":"Exploit-DB (https://gitlab.com/exploit-database/exploitdb)","entries":[]},"verdict":{"level":"low","text":"Lower severity and a low EPSS score (0.14%). Track it; it rarely justifies an emergency change on its own."},"changes":[],"references":[{"url":"https://git.kernel.org/stable/c/269c800a7a7e363459291885b35f7bc72e231ed6","tags":["Patch"],"source":"416baaa9-dc9f-4396-8d5f-8c081fb06d67"},{"url":"https://git.kernel.org/stable/c/6c8c44e6553b9f072f62d9875e567766eb293162","tags":["Patch"],"source":"416baaa9-dc9f-4396-8d5f-8c081fb06d67"},{"url":"https://git.kernel.org/stable/c/745a535461bbb90a56d9357573c9f97a5c12abe1","tags":["Patch"],"source":"416baaa9-dc9f-4396-8d5f-8c081fb06d67"},{"url":"https://git.kernel.org/stable/c/ad0057fb91218914d6c98268718ceb9d59b388e1","tags":["Patch"],"source":"416baaa9-dc9f-4396-8d5f-8c081fb06d67"},{"url":"https://git.kernel.org/stable/c/ae9cdb29efed20ffdee9ff3b0bb72fb369c353da","source":"416baaa9-dc9f-4396-8d5f-8c081fb06d67"},{"url":"https://git.kernel.org/stable/c/bd4a7fb04f06f419b0e93d8b52fe32067eb312d1","source":"416baaa9-dc9f-4396-8d5f-8c081fb06d67"},{"url":"https://git.kernel.org/stable/c/dd53414e301beb915fe672dc4c4a51bafb917604","tags":["Patch"],"source":"416baaa9-dc9f-4396-8d5f-8c081fb06d67"},{"url":"https://git.kernel.org/stable/c/dd577cb55588ec3fbc66af3621280306601c4192","tags":["Patch"],"source":"416baaa9-dc9f-4396-8d5f-8c081fb06d67"}],"sources":{"nvd":"https://nvd.nist.gov/vuln/detail/CVE-2026-31610","epss":"https://www.first.org/epss/","kev":"https://www.cisa.gov/known-exploited-vulnerabilities-catalog","exploitdb":"https://www.exploit-db.com/"},"licence":"CC BY 4.0 — link back to the CVE Explorer if you publish the results; upstream data remains subject to its own terms."}