{"id":"CVE-2026-98438","title":"mptcp: options: fix uninit-value in mptcp_write_data_fin","summary":"In the Linux kernel, the following vulnerability has been resolved:\n\nmptcp: options: fix uninit-value in mptcp_write_data_fin\n\nWhen sending a DATA_FIN without data, and because the DATA_FIN occupies\n1 octet of the connection-level sequen…","severity":"none","vendor":"Linux","product":"Linux","affected":["Linux >= cfcceb7a39fc10a6f896af8229bf81d96acb22cc < 9a682067dd7b9dce6b94a0a05661dcc921446402","Linux >= cfcceb7a39fc10a6f896af8229bf81d96acb22cc < b110f1dd6cb6a9930503354a01a315e0a821eaa7","Linux 7.1"],"published":"2026-10-18","updated":"2026-10-18","sourceUpdated":"2026-10-18T14:45:27.288Z","source":"CVEORG","sourceUrl":"https://www.cve.org/CVERecord?id=CVE-2026-98438","references":[{"url":"https://git.kernel.org/stable/c/9a682067dd7b9dce6b94a0a05661dcc921446402"},{"url":"https://git.kernel.org/stable/c/b110f1dd6cb6a9930503354a01a315e0a821eaa7"}],"tags":["cve.org"],"ingestedAt":"2026-10-18T15:45:12.310Z","slug":"CVE-2026-98438","body":"## Overview\n\nIn the Linux kernel, the following vulnerability has been resolved:\n\nmptcp: options: fix uninit-value in mptcp_write_data_fin\n\nWhen sending a DATA_FIN without data, and because the DATA_FIN occupies\n1 octet of the connection-level sequence space [1], it is then required\nto add a DSS mapping with specific values.\n\nIf the checksum has been negotiated, it also needs to be computed, and\nincluded in the outgoing packet, and thus the initial csum data needs to\nbe reset to 0 as well. This is no longer the case since commit\ncfcceb7a39fc (\"tcp: shrink per-packet memset in __tcp_transmit_skb()\"),\nbecause the whole ext_copy structure is no longer zeroed by default.\n\nThis seems to be the only case where use_map is changed and set\nafterwards, so initialising the csum field only in this case, along with\nother fields for this specific case.\n\n## Affected\n\n- `Linux >= cfcceb7a39fc10a6f896af8229bf81d96acb22cc < 9a682067dd7b9dce6b94a0a05661dcc921446402`\n- `Linux >= cfcceb7a39fc10a6f896af8229bf81d96acb22cc < b110f1dd6cb6a9930503354a01a315e0a821eaa7`\n- `Linux 7.1`\n\n## Remediation\n\nRefer to the linked advisories for vendor-supplied fixes and affected version ranges.","depth":"sunlit","depthScore":3,"depthScoreParts":{"impact":2.8,"likelihood":0,"exploitation":0,"ransomware":0},"changes":[]}