{"id":"CVE-2026-63996","summary":"ethtool: cmis: require exact CDB reply length","details":"In the Linux kernel, the following vulnerability has been resolved:\n\nethtool: cmis: require exact CDB reply length\n\nMalicious SFP module could respond with rpl_len longer than\nwhat cmis_cdb_process_reply() expected, leading to OOB writes.\nMalicious HW is a bit theoretical but some modules may just\nbe buggy and/or the reads may occasionally get corrupted,\nso let's protect the kernel.\n\nThe existing check protects from short replies. We need to\nprotect from long ones, too. All callers that pass a non-zero\nrpl_exp_len cast the reply payload to a fixed-layout struct\nand read fields at fixed offsets, with no version negotiation\nor short-reply handling:\n\n  - cmis_cdb_validate_password()\n  - cmis_cdb_module_features_get()\n  - cmis_fw_update_fw_mng_features_get()\n\nso let's assume that responses longer than expected do not\nhave to be handled gracefully here. Add a warning message\nto make the debug easier in case my understanding is wrong...\n\nNote that page_data-\u003elength (argument of kmalloc) comes from\nlast arg to ethtool_cmis_page_init() which is rpl_exp_len.\n\nNote2 that AIs also like to point out overflows in args-\u003ereq.payload\nitself (which is a fixed-size 120 B buffer, on the stack),\nbut callers should be reading structs defined by the standard,\nso protecting from requests for more data than max seem like\ndefensive programming.","modified":"2026-07-22T03:32:07.039768430Z","published":"2026-07-19T14:56:15.256Z","database_specific":{"cna_assigner":"Linux","osv_generated_from":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/63xxx/CVE-2026-63996.json"},"references":[{"type":"WEB","url":"https://git.kernel.org/stable/c/2f818cc98fd2c63a08239cb48995f6c3bfe9d9b3"},{"type":"WEB","url":"https://git.kernel.org/stable/c/4d42fb88ec61f2e98c33a9e3a2de371d5edbc6b1"},{"type":"WEB","url":"https://git.kernel.org/stable/c/6c3f999a9d1338c6c89a9ff4549eafe72bc2e7b1"},{"type":"WEB","url":"https://git.kernel.org/stable/c/eb5dcd740cd7fa27bc2caeff2d28ef28e93ff4d3"},{"type":"ADVISORY","url":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/63xxx/CVE-2026-63996.json"},{"type":"ADVISORY","url":"https://nvd.nist.gov/vuln/detail/CVE-2026-63996"},{"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":"a39c84d796254e6b1662ca0c46dbc313379e9291"},{"fixed":"2f818cc98fd2c63a08239cb48995f6c3bfe9d9b3"},{"fixed":"4d42fb88ec61f2e98c33a9e3a2de371d5edbc6b1"},{"fixed":"eb5dcd740cd7fa27bc2caeff2d28ef28e93ff4d3"},{"fixed":"6c3f999a9d1338c6c89a9ff4549eafe72bc2e7b1"}]}],"database_specific":{"source":"https://storage.googleapis.com/osv-test-cve-osv-conversion/osv-output/CVE-2026-63996.json"}},{"package":{"name":"Kernel","ecosystem":"Linux"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"6.11.0"},{"fixed":"6.12.93"}]},{"type":"ECOSYSTEM","events":[{"introduced":"6.13.0"},{"fixed":"6.18.35"}]},{"type":"ECOSYSTEM","events":[{"introduced":"6.19.0"},{"fixed":"7.0.12"}]}],"database_specific":{"source":"https://storage.googleapis.com/osv-test-cve-osv-conversion/osv-output/CVE-2026-63996.json"}}],"schema_version":"1.7.5","severity":[{"type":"CVSS_V3","score":"CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H"}]}