{ "dataType": "CVE_RECORD", "dataVersion": "5.2", "cveMetadata": { "cveId": "CVE-2026-63996", "assignerOrgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "state": "PUBLISHED", "assignerShortName": "Linux", "dateReserved": "2026-07-19T07:54:57.026Z", "datePublished": "2026-07-19T14:56:15.256Z", "dateUpdated": "2026-08-05T12:38:00.530Z" }, "containers": { "cna": { "providerMetadata": { "orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "shortName": "Linux", "dateUpdated": "2026-08-05T12:38:00.530Z" }, "descriptions": [ { "lang": "en", "value": "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->length (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->req.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." } ], "metrics": [ { "cvssV3_1": { "version": "3.1", "vectorString": "CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H", "baseScore": 7.8, "baseSeverity": "HIGH" }, "scenarios": [ { "lang": "en", "value": "AV:L - The vulnerable code is reached only via the local ethtool genetlink firmware-flash path (ETHTOOL_MSG_MODULE_FW_FLASH_ACT), not from remote network input; a malicious transceiver supplies the malformed CDB reply once that local ioctl-like operation is invoked.\nAC:L - A malicious CMIS module can reliably set rpl_len up to 255 on CDB replies; no race or uncontrollable memory layout is required, and an attacker with CAP_NET_ADMIN can bring the netdev down and initiate flashing deterministically.\nPR:L - Triggering module firmware flash requires CAP_NET_ADMIN, which is enforced via GENL_UNS_ADMIN_PERM/netlink_ns_capable and is obtainable by unprivileged users inside a user namespace (unshare -Urn), not only by init-namespace root.\nUI:N - Exploitation does not require a separate victim user action beyond the attacker (or compromised local process with CAP_NET_ADMIN) issuing the ethtool module firmware-flash command; no interactive victim steps are needed.\nS:U - Impact is kernel stack corruption and potential privilege escalation or denial of service within the same kernel security boundary; this is not a VM escape, sandbox escape, or cross-authority boundary crossing.\nC:H - The out-of-bounds stack write corrupts adjacent kernel stack memory and can be leveraged for arbitrary kernel memory disclosure; related CMIS ethtool bugs in the same path have already caused demonstrable stack corruption.\nI:H - memcpy() can write up to 135 bytes past the 120-byte payload buffer on the kernel stack, enabling control-data corruption and potential arbitrary kernel code execution, not merely a bounded modification.\nA:H - Stack corruption in this CMIS firmware-flash workqueue path can trigger kernel oops/panic (as seen in the related CVE-2025-37791 stack-protector failure in the same call chain) or hang the affected system." } ] } ], "affected": [ { "product": "Linux", "vendor": "Linux", "defaultStatus": "unaffected", "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git", "programFiles": [ "net/ethtool/cmis_cdb.c" ], "versions": [ { "version": "a39c84d796254e6b1662ca0c46dbc313379e9291", "lessThan": "2f818cc98fd2c63a08239cb48995f6c3bfe9d9b3", "status": "affected", "versionType": "git" }, { "version": "a39c84d796254e6b1662ca0c46dbc313379e9291", "lessThan": "4d42fb88ec61f2e98c33a9e3a2de371d5edbc6b1", "status": "affected", "versionType": "git" }, { "version": "a39c84d796254e6b1662ca0c46dbc313379e9291", "lessThan": "eb5dcd740cd7fa27bc2caeff2d28ef28e93ff4d3", "status": "affected", "versionType": "git" }, { "version": "a39c84d796254e6b1662ca0c46dbc313379e9291", "lessThan": "6c3f999a9d1338c6c89a9ff4549eafe72bc2e7b1", "status": "affected", "versionType": "git" } ] }, { "product": "Linux", "vendor": "Linux", "defaultStatus": "affected", "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git", "programFiles": [ "net/ethtool/cmis_cdb.c" ], "versions": [ { "version": "6.11", "status": "affected" }, { "version": "0", "lessThan": "6.11", "status": "unaffected", "versionType": "semver" }, { "version": "6.12.93", "lessThanOrEqual": "6.12.*", "status": "unaffected", "versionType": "semver" }, { "version": "6.18.35", "lessThanOrEqual": "6.18.*", "status": "unaffected", "versionType": "semver" }, { "version": "7.0.12", "lessThanOrEqual": "7.0.*", "status": "unaffected", "versionType": "semver" }, { "version": "7.1", "lessThanOrEqual": "*", "status": "unaffected", "versionType": "original_commit_for_fix" } ] } ], "cpeApplicability": [ { "nodes": [ { "operator": "OR", "negate": false, "cpeMatch": [ { "vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "6.11", "versionEndExcluding": "6.12.93" }, { "vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "6.11", "versionEndExcluding": "6.18.35" }, { "vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "6.11", "versionEndExcluding": "7.0.12" }, { "vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "6.11", "versionEndExcluding": "7.1" } ] } ] } ], "references": [ { "url": "https://git.kernel.org/stable/c/2f818cc98fd2c63a08239cb48995f6c3bfe9d9b3" }, { "url": "https://git.kernel.org/stable/c/4d42fb88ec61f2e98c33a9e3a2de371d5edbc6b1" }, { "url": "https://git.kernel.org/stable/c/eb5dcd740cd7fa27bc2caeff2d28ef28e93ff4d3" }, { "url": "https://git.kernel.org/stable/c/6c3f999a9d1338c6c89a9ff4549eafe72bc2e7b1" } ], "title": "ethtool: cmis: require exact CDB reply length", "x_generator": { "engine": "bippy-1.2.0" } } } }