{"id":"CVE-2026-99083","title":"ksmbd: fix heap out-of-bounds write in krb5_authenticate()","summary":"In the Linux kernel, the following vulnerability has been resolved:\n\nksmbd: fix heap out-of-bounds write in krb5_authenticate()\n\nIn krb5_authenticate(), out_len is calculated to determine available\nheadroom in response_buf for the incomi…","severity":"high","cvss":8.8,"cvssVector":"CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H","cvssSource":"cna","vendor":"Linux","product":"Linux","affected":["Linux >= 98422bdd4cb3ca4d08844046f6507d7ec2c2b8d8 < 59c6dcc5dd9dafe764ca0d40525933b2be69b059","Linux >= 98422bdd4cb3ca4d08844046f6507d7ec2c2b8d8 < 80af1bde97d5a85ad6f2c40ca894ccc8fa75a27a","Linux >= 98422bdd4cb3ca4d08844046f6507d7ec2c2b8d8 < 517404e157395d0f8da125ca956c566895dfcd06","Linux >= 98422bdd4cb3ca4d08844046f6507d7ec2c2b8d8 < 4722d06b2907585074252061b1024a696c1cfc23","Linux >= 98422bdd4cb3ca4d08844046f6507d7ec2c2b8d8 < 23a0be6a84a38ac169eeab49017934e8e27c65f0","Linux 676392184785ace61e939831e7ca44a03d438c3b","Linux ef572ffa8eb44111eed2925fbb2adca78bdcbf61","Linux 2ba03cecb12ac7ac9e0170e251543c56832d9959","Linux >= 5.15.145 < 5.16","Linux >= 6.1.40 < 6.2","Linux >= 6.4.5 < 6.5","Linux 6.5"],"published":"2026-10-23","updated":"2026-10-26","sourceUpdated":"2026-10-26T06:56:58.783Z","source":"CVEORG","sourceUrl":"https://www.cve.org/CVERecord?id=CVE-2026-99083","references":[{"url":"https://git.kernel.org/stable/c/59c6dcc5dd9dafe764ca0d40525933b2be69b059"},{"url":"https://git.kernel.org/stable/c/80af1bde97d5a85ad6f2c40ca894ccc8fa75a27a"},{"url":"https://git.kernel.org/stable/c/517404e157395d0f8da125ca956c566895dfcd06"},{"url":"https://git.kernel.org/stable/c/4722d06b2907585074252061b1024a696c1cfc23"},{"url":"https://git.kernel.org/stable/c/23a0be6a84a38ac169eeab49017934e8e27c65f0"}],"tags":["cve.org"],"epss":0.00408,"epssPercentile":0.34885,"ingestedAt":"2026-10-23T13:24:55.512Z","slug":"CVE-2026-99083","body":"## Overview\n\nIn the Linux kernel, the following vulnerability has been resolved:\n\nksmbd: fix heap out-of-bounds write in krb5_authenticate()\n\nIn krb5_authenticate(), out_len is calculated to determine available\nheadroom in response_buf for the incoming Kerberos AP-REP token. However,\nwhen SMB2_SESSION_SETUP is processed as a non-first element of a compounded\nSMB2 request, the calculation omits work->next_smb2_rsp_hdr_off.\n\nThis causes out_len to overstate remaining buffer headroom by\nthe cumulative size of prior responses in the compound chain. Consequently,\nthe length check in ksmbd_krb5_authenticate()\n(*out_len <= resp->spnego_blob_len) passes erroneously, allowing memcpy()\nto write the AP-REP blob past the end of response_buf into adjacent kernel\nheap memory.\n\nFix this by subtracting work->next_smb2_rsp_hdr_off when computing out_len,\nensuring it accurately reflects physical remaining buffer space.\n\n## Affected\n\n- `Linux >= 98422bdd4cb3ca4d08844046f6507d7ec2c2b8d8 < 59c6dcc5dd9dafe764ca0d40525933b2be69b059`\n- `Linux >= 98422bdd4cb3ca4d08844046f6507d7ec2c2b8d8 < 80af1bde97d5a85ad6f2c40ca894ccc8fa75a27a`\n- `Linux >= 98422bdd4cb3ca4d08844046f6507d7ec2c2b8d8 < 517404e157395d0f8da125ca956c566895dfcd06`\n- `Linux >= 98422bdd4cb3ca4d08844046f6507d7ec2c2b8d8 < 4722d06b2907585074252061b1024a696c1cfc23`\n- `Linux >= 98422bdd4cb3ca4d08844046f6507d7ec2c2b8d8 < 23a0be6a84a38ac169eeab49017934e8e27c65f0`\n- `Linux 676392184785ace61e939831e7ca44a03d438c3b`\n- `Linux ef572ffa8eb44111eed2925fbb2adca78bdcbf61`\n- `Linux 2ba03cecb12ac7ac9e0170e251543c56832d9959`\n- `Linux >= 5.15.145 < 5.16`\n- `Linux >= 6.1.40 < 6.2`\n- `Linux >= 6.4.5 < 6.5`\n- `Linux 6.5`\n\n## Remediation\n\nRefer to the linked advisories for vendor-supplied fixes and affected version ranges.","depth":"twilight","depthScore":48,"depthScoreParts":{"impact":48.4,"likelihood":0.1,"exploitation":0,"ransomware":0},"changes":[{"seq":228814,"id":"CVE-2026-99083","ts":1792854080810,"field":"cvss","old":null,"new":"8.8"},{"seq":228813,"id":"CVE-2026-99083","ts":1792854080810,"field":"severity","old":"none","new":"high"}]}