{"id":"CVE-2026-31610","state":"PUBLISHED","title":"ksmbd: fix mechToken leak when SPNEGO decode fails after token alloc","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.","publishedAt":"2026-04-24T14:42:31.471Z","updatedAt":"2026-07-24T14:33:31.688Z","severity":null,"assigner":"Linux","products":["Linux Linux"],"affected":[{"vendor":"Linux","product":"Linux","defaultStatus":"unaffected","versions":[{"version":"fad4161b5cd01a24202234976ebbb133f7adc0b5","status":"affected","lessThan":"ae9cdb29efed20ffdee9ff3b0bb72fb369c353da","versionType":"git"},{"version":"fad4161b5cd01a24202234976ebbb133f7adc0b5","status":"affected","lessThan":"bd4a7fb04f06f419b0e93d8b52fe32067eb312d1","versionType":"git"},{"version":"fad4161b5cd01a24202234976ebbb133f7adc0b5","status":"affected","lessThan":"745a535461bbb90a56d9357573c9f97a5c12abe1","versionType":"git"},{"version":"fad4161b5cd01a24202234976ebbb133f7adc0b5","status":"affected","lessThan":"dd577cb55588ec3fbc66af3621280306601c4192","versionType":"git"},{"version":"fad4161b5cd01a24202234976ebbb133f7adc0b5","status":"affected","lessThan":"dd53414e301beb915fe672dc4c4a51bafb917604","versionType":"git"},{"version":"fad4161b5cd01a24202234976ebbb133f7adc0b5","status":"affected","lessThan":"269c800a7a7e363459291885b35f7bc72e231ed6","versionType":"git"},{"version":"fad4161b5cd01a24202234976ebbb133f7adc0b5","status":"affected","lessThan":"6c8c44e6553b9f072f62d9875e567766eb293162","versionType":"git"},{"version":"fad4161b5cd01a24202234976ebbb133f7adc0b5","status":"affected","lessThan":"ad0057fb91218914d6c98268718ceb9d59b388e1","versionType":"git"}],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["fs/smb/server/connection.c","fs/smb/server/smb2pdu.c"]},{"vendor":"Linux","product":"Linux","defaultStatus":"affected","versions":[{"version":"5.15","status":"affected"},{"version":"0","status":"unaffected","lessThan":"5.15","versionType":"semver"},{"version":"5.15.212","status":"unaffected","lessThanOrEqual":"5.15.*","versionType":"semver"},{"version":"6.1.178","status":"unaffected","lessThanOrEqual":"6.1.*","versionType":"semver"},{"version":"6.6.136","status":"unaffected","lessThanOrEqual":"6.6.*","versionType":"semver"},{"version":"6.12.83","status":"unaffected","lessThanOrEqual":"6.12.*","versionType":"semver"},{"version":"6.18.24","status":"unaffected","lessThanOrEqual":"6.18.*","versionType":"semver"},{"version":"6.19.14","status":"unaffected","lessThanOrEqual":"6.19.*","versionType":"semver"},{"version":"7.0.1","status":"unaffected","lessThanOrEqual":"7.0.*","versionType":"semver"},{"version":"7.1","status":"unaffected","lessThanOrEqual":"*","versionType":"original_commit_for_fix"}],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["fs/smb/server/connection.c","fs/smb/server/smb2pdu.c"]}],"references":["https://git.kernel.org/stable/c/ae9cdb29efed20ffdee9ff3b0bb72fb369c353da","https://git.kernel.org/stable/c/bd4a7fb04f06f419b0e93d8b52fe32067eb312d1","https://git.kernel.org/stable/c/745a535461bbb90a56d9357573c9f97a5c12abe1","https://git.kernel.org/stable/c/dd577cb55588ec3fbc66af3621280306601c4192","https://git.kernel.org/stable/c/dd53414e301beb915fe672dc4c4a51bafb917604","https://git.kernel.org/stable/c/269c800a7a7e363459291885b35f7bc72e231ed6","https://git.kernel.org/stable/c/6c8c44e6553b9f072f62d9875e567766eb293162","https://git.kernel.org/stable/c/ad0057fb91218914d6c98268718ceb9d59b388e1"],"weaknesses":[],"ingestedAt":"2026-10-29T20:11:40.391Z","source":{"repository":"CVEProject/cvelistV5","path":"cves/2026/31xxx/CVE-2026-31610.json","commit":"556c9d3a8cd17e218bb8e452ba7cd619a384ff47"},"raw":{"dataType":"CVE_RECORD","dataVersion":"5.2","cveMetadata":{"cveId":"CVE-2026-31610","state":"PUBLISHED","datePublished":"2026-04-24T14:42:31.471Z","dateUpdated":"2026-07-24T14:33:31.688Z","assignerShortName":"Linux","assignerOrgId":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","dateReserved":"2026-03-09T15:48:24.122Z"},"containers":{"cna":{"title":"ksmbd: fix mechToken leak when SPNEGO decode fails after token alloc","descriptions":[{"lang":"en","value":"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."}],"affected":[{"vendor":"Linux","product":"Linux","defaultStatus":"unaffected","versions":[{"version":"fad4161b5cd01a24202234976ebbb133f7adc0b5","status":"affected","lessThan":"ae9cdb29efed20ffdee9ff3b0bb72fb369c353da","versionType":"git"},{"version":"fad4161b5cd01a24202234976ebbb133f7adc0b5","status":"affected","lessThan":"bd4a7fb04f06f419b0e93d8b52fe32067eb312d1","versionType":"git"},{"version":"fad4161b5cd01a24202234976ebbb133f7adc0b5","status":"affected","lessThan":"745a535461bbb90a56d9357573c9f97a5c12abe1","versionType":"git"},{"version":"fad4161b5cd01a24202234976ebbb133f7adc0b5","status":"affected","lessThan":"dd577cb55588ec3fbc66af3621280306601c4192","versionType":"git"},{"version":"fad4161b5cd01a24202234976ebbb133f7adc0b5","status":"affected","lessThan":"dd53414e301beb915fe672dc4c4a51bafb917604","versionType":"git"},{"version":"fad4161b5cd01a24202234976ebbb133f7adc0b5","status":"affected","lessThan":"269c800a7a7e363459291885b35f7bc72e231ed6","versionType":"git"},{"version":"fad4161b5cd01a24202234976ebbb133f7adc0b5","status":"affected","lessThan":"6c8c44e6553b9f072f62d9875e567766eb293162","versionType":"git"},{"version":"fad4161b5cd01a24202234976ebbb133f7adc0b5","status":"affected","lessThan":"ad0057fb91218914d6c98268718ceb9d59b388e1","versionType":"git"}],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["fs/smb/server/connection.c","fs/smb/server/smb2pdu.c"]},{"vendor":"Linux","product":"Linux","defaultStatus":"affected","versions":[{"version":"5.15","status":"affected"},{"version":"0","status":"unaffected","lessThan":"5.15","versionType":"semver"},{"version":"5.15.212","status":"unaffected","lessThanOrEqual":"5.15.*","versionType":"semver"},{"version":"6.1.178","status":"unaffected","lessThanOrEqual":"6.1.*","versionType":"semver"},{"version":"6.6.136","status":"unaffected","lessThanOrEqual":"6.6.*","versionType":"semver"},{"version":"6.12.83","status":"unaffected","lessThanOrEqual":"6.12.*","versionType":"semver"},{"version":"6.18.24","status":"unaffected","lessThanOrEqual":"6.18.*","versionType":"semver"},{"version":"6.19.14","status":"unaffected","lessThanOrEqual":"6.19.*","versionType":"semver"},{"version":"7.0.1","status":"unaffected","lessThanOrEqual":"7.0.*","versionType":"semver"},{"version":"7.1","status":"unaffected","lessThanOrEqual":"*","versionType":"original_commit_for_fix"}],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["fs/smb/server/connection.c","fs/smb/server/smb2pdu.c"]}],"references":[{"url":"https://git.kernel.org/stable/c/ae9cdb29efed20ffdee9ff3b0bb72fb369c353da"},{"url":"https://git.kernel.org/stable/c/bd4a7fb04f06f419b0e93d8b52fe32067eb312d1"},{"url":"https://git.kernel.org/stable/c/745a535461bbb90a56d9357573c9f97a5c12abe1"},{"url":"https://git.kernel.org/stable/c/dd577cb55588ec3fbc66af3621280306601c4192"},{"url":"https://git.kernel.org/stable/c/dd53414e301beb915fe672dc4c4a51bafb917604"},{"url":"https://git.kernel.org/stable/c/269c800a7a7e363459291885b35f7bc72e231ed6"},{"url":"https://git.kernel.org/stable/c/6c8c44e6553b9f072f62d9875e567766eb293162"},{"url":"https://git.kernel.org/stable/c/ad0057fb91218914d6c98268718ceb9d59b388e1"}],"providerMetadata":{"shortName":"Linux","orgId":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","dateUpdated":"2026-07-24T14:33:31.688Z"},"cpeApplicability":[{"nodes":[{"operator":"OR","negate":false,"cpeMatch":[{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"5.15","versionEndExcluding":"5.15.212"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"5.15","versionEndExcluding":"6.1.178"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"5.15","versionEndExcluding":"6.6.136"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"5.15","versionEndExcluding":"6.12.83"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"5.15","versionEndExcluding":"6.18.24"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"5.15","versionEndExcluding":"6.19.14"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"5.15","versionEndExcluding":"7.0.1"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"5.15","versionEndExcluding":"7.1"}]}]}],"x_generator":{"engine":"bippy-1.2.0"}}}}}