{"id":"CVE-2026-64102","title":"RDMA/siw: Reject MPA FPDU length underflow before signed receive math","summary":"In the Linux kernel, the following vulnerability has been resolved:\n\nRDMA/siw: Reject MPA FPDU length underflow before signed receive math\n\nA malicious connected siw peer can send an iWARP FPDU whose MPA length\nfield (c_hdr->mpa_len, 16 …","severity":"critical","cvss":9.8,"cvssVector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H","cvssSource":"cna","vendor":"Linux","product":"Linux","affected":["Linux >= 8b6a361b8c482f22ac99c3273285ff16b23fba91 < 683f7cfbf514193d63c0efa079f3352bde84c2e0","Linux >= 8b6a361b8c482f22ac99c3273285ff16b23fba91 < 4a331582011d9e8089af8aa2a61ec6b4443bb245","Linux >= 8b6a361b8c482f22ac99c3273285ff16b23fba91 < 33a8b5e971e294ec2a7b74211c545e09efd8e9ac","Linux >= 8b6a361b8c482f22ac99c3273285ff16b23fba91 < 14553be882d9ce91749c9d64041de66e34ad8e70","Linux >= 8b6a361b8c482f22ac99c3273285ff16b23fba91 < c7c0c0f4379dedec12d24dbb9dded5d2db7fd9f2","Linux >= 8b6a361b8c482f22ac99c3273285ff16b23fba91 < 1012896f4225e8f801ff3c1648023845b66dfb11","Linux >= 8b6a361b8c482f22ac99c3273285ff16b23fba91 < 775b4dc9618a99a1fa48b57554041a5dc17e1336","Linux >= 8b6a361b8c482f22ac99c3273285ff16b23fba91 < 0ce1bc9e46ecabe84772bb561e373c0d9876d6f2","Linux 5.3"],"ssvc":{"exploitation":"none","automatable":"yes","technicalImpact":"total","timestamp":"2026-10-16T15:36:18.801204Z"},"published":"2026-07-19","updated":"2026-10-16","sourceUpdated":"2026-10-16T15:42:22.150Z","source":"CVEORG","sourceUrl":"https://www.cve.org/CVERecord?id=CVE-2026-64102","references":[{"url":"https://git.kernel.org/stable/c/683f7cfbf514193d63c0efa079f3352bde84c2e0"},{"url":"https://git.kernel.org/stable/c/4a331582011d9e8089af8aa2a61ec6b4443bb245"},{"url":"https://git.kernel.org/stable/c/33a8b5e971e294ec2a7b74211c545e09efd8e9ac"},{"url":"https://git.kernel.org/stable/c/14553be882d9ce91749c9d64041de66e34ad8e70"},{"url":"https://git.kernel.org/stable/c/c7c0c0f4379dedec12d24dbb9dded5d2db7fd9f2"},{"url":"https://git.kernel.org/stable/c/1012896f4225e8f801ff3c1648023845b66dfb11"},{"url":"https://git.kernel.org/stable/c/775b4dc9618a99a1fa48b57554041a5dc17e1336"},{"url":"https://git.kernel.org/stable/c/0ce1bc9e46ecabe84772bb561e373c0d9876d6f2"}],"tags":["cve.org"],"epss":0.005,"epssPercentile":0.41477,"ingestedAt":"2026-10-16T17:24:46.804Z","slug":"CVE-2026-64102","body":"## Overview\n\nIn the Linux kernel, the following vulnerability has been resolved:\n\nRDMA/siw: Reject MPA FPDU length underflow before signed receive math\n\nA malicious connected siw peer can send an iWARP FPDU whose MPA length\nfield (c_hdr->mpa_len, 16 bit big-endian, peer-controlled) is smaller\nthan the fixed DDP/RDMAP header for the announced opcode. Soft-iWARP\nparses the full header in siw_get_hdr() based on iwarp_pktinfo[opcode]\n.hdr_len, but never compares mpa_len against that header length.\n\nsiw_tcp_rx_data() then derives\n\n    srx->fpdu_part_rem = be16_to_cpu(mpa_len) - fpdu_part_rcvd\n                         + MPA_HDR_SIZE;\n\nwhere fpdu_part_rcvd equals iwarp_pktinfo[opcode].hdr_len at this\npoint. For a tagged WRITE (hdr_len 16, MPA_HDR_SIZE 2) the smallest\non-wire mpa_len of 0 yields fpdu_part_rem = -14, and any mpa_len below\nhdr_len - MPA_HDR_SIZE underflows to a negative int.\n\nThe signed value then flows into siw_proc_write()/siw_proc_rresp() as\n\n    bytes = min(srx->fpdu_part_rem, srx->skb_new);\n\nis handed to siw_check_mem() as an int len (whose interval check\naddr + len > mem->va + mem->len is satisfied for a valid base when\nlen is negative), and reaches siw_rx_data() -> siw_rx_kva() /\nsiw_rx_umem() -> skb_copy_bits() as a signed copy length. The header\ncopy branch in skb_copy_bits() promotes that to size_t, producing a\nmulti-gigabyte read.\n\nKASAN under a KUnit harness that drives the real kernel TCP receive\npath -- a loopback AF_INET socketpair, the malformed FPDU written via\nkernel_sendmsg, sk_data_ready firing in softirq, tcp_read_sock\ndispatching to siw_tcp_rx_data -- reports:\n\n    BUG: KASAN: use-after-free in skb_copy_bits+0x284/0x480\n    Read of size 4294967295 at addr ffff888...\n    Call Trace:\n     skb_copy_bits\n     siw_rx_kva\n     siw_rx_data\n     siw_check_mem\n     siw_proc_write\n     siw_tcp_rx_data\n     __tcp_read_sock\n     siw_qp_llp_data_ready\n     tcp_data_ready\n     tcp_data_queue\n\nAdd the missing invariant at the earliest point where the peer header\nis fully assembled. iwarp_pktinfo[*].hdr_len - MPA_HDR_SIZE is exactly\nthe value the siw transmitter uses as the minimum mpa_len for each\nopcode (drivers/infiniband/sw/siw/siw_qp.c:33), so this matches the\nprotocol contract. Out-of-range FPDUs terminate the connection with\nTERM_ERROR_LAYER_LLP / LLP_ETYPE_MPA / LLP_ECODE_FPDU_START -- which\nis RFC 5044 Section 8 error code 3 (\"Marker and ULPDU Length fields\ndo not agree on the start of an FPDU\"), the correct framing-error\nclass for this inconsistency.\n\n## Affected\n\n- `Linux >= 8b6a361b8c482f22ac99c3273285ff16b23fba91 < 683f7cfbf514193d63c0efa079f3352bde84c2e0`\n- `Linux >= 8b6a361b8c482f22ac99c3273285ff16b23fba91 < 4a331582011d9e8089af8aa2a61ec6b4443bb245`\n- `Linux >= 8b6a361b8c482f22ac99c3273285ff16b23fba91 < 33a8b5e971e294ec2a7b74211c545e09efd8e9ac`\n- `Linux >= 8b6a361b8c482f22ac99c3273285ff16b23fba91 < 14553be882d9ce91749c9d64041de66e34ad8e70`\n- `Linux >= 8b6a361b8c482f22ac99c3273285ff16b23fba91 < c7c0c0f4379dedec12d24dbb9dded5d2db7fd9f2`\n- `Linux >= 8b6a361b8c482f22ac99c3273285ff16b23fba91 < 1012896f4225e8f801ff3c1648023845b66dfb11`\n- `Linux >= 8b6a361b8c482f22ac99c3273285ff16b23fba91 < 775b4dc9618a99a1fa48b57554041a5dc17e1336`\n- `Linux >= 8b6a361b8c482f22ac99c3273285ff16b23fba91 < 0ce1bc9e46ecabe84772bb561e373c0d9876d6f2`\n- `Linux 5.3`\n\n## Remediation\n\nRefer to the linked advisories for vendor-supplied fixes and affected version ranges.","depth":"midnight","depthScore":54,"depthScoreParts":{"impact":53.9,"likelihood":0.1,"exploitation":0,"ransomware":0},"changes":[]}