CVE-2026-64102RDMA/siw: Reject MPA FPDU length underflow before signed receive math
- 9.8CriticalCVSS base score
- 0.50%Exploitation in 30 daysEPSS · top 57% of all CVEs
- NoKnown exploitednot in CISA's KEV catalog
- NonePublic exploitsnone known yet
Description
In the Linux kernel, the following vulnerability has been resolved: RDMA/siw: Reject MPA FPDU length underflow before signed receive math A malicious connected siw peer can send an iWARP FPDU whose MPA length field (c_hdr->mpa_len, 16 bit big-endian, peer-controlled) is smaller than the fixed DDP/RDMAP header for the announced opcode. Soft-iWARP parses the full header in siw_get_hdr() based on iwarp_pktinfo[opcode] .hdr_len, but never compares mpa_len against that header length. siw_tcp_rx_data() then derives srx->fpdu_part_rem = be16_to_cpu(mpa_len) - fpdu_part_rcvd + MPA_HDR_SIZE; where fpdu_part_rcvd equals iwarp_pktinfo[opcode].hdr_len at this point. For a tagged WRITE (hdr_len 16, MPA_HDR_SIZE 2) the smallest on-wire mpa_len of 0 yields fpdu_part_rem = -14, and any mpa_len below hdr_len - MPA_HDR_SIZE underflows to a negative int. The signed value then flows into siw_proc_write()/siw_proc_rresp() as bytes = min(srx->fpdu_part_rem, srx->skb_new); is handed to siw_check_mem() as an int len (whose interval check addr + len > mem->va + mem->len is satisfied for a valid base when len is negative), and reaches siw_rx_data() -> siw_rx_kva() / siw_rx_umem() -> skb_copy_bits() as a signed copy length. The header copy branch in skb_copy_bits() promotes that to size_t, producing a multi-gigabyte read. KASAN under a KUnit harness that drives the real kernel TCP receive path -- a loopback AF_INET socketpair, the malformed FPDU written via kernel_sendmsg, sk_data_ready firing in softirq, tcp_read_sock dispatching to siw_tcp_rx_data -- reports: BUG: KASAN: use-after-free in skb_copy_bits+0x284/0x480 Read of size 4294967295 at addr ffff888... Call Trace: skb_copy_bits siw_rx_kva siw_rx_data siw_check_mem siw_proc_write siw_tcp_rx_data __tcp_read_sock siw_qp_llp_data_ready tcp_data_ready tcp_data_queue Add the missing invariant at the earliest point where the peer header is fully assembled. iwarp_pktinfo[*].hdr_len - MPA_HDR_SIZE is exactly the value the siw transmitter uses as the minimum mpa_len for each opcode (drivers/infiniband/sw/siw/siw_qp.c:33), so this matches the protocol contract. Out-of-range FPDUs terminate the connection with TERM_ERROR_LAYER_LLP / LLP_ETYPE_MPA / LLP_ECODE_FPDU_START -- which is RFC 5044 Section 8 error code 3 ("Marker and ULPDU Length fields do not agree on the start of an FPDU"), the correct framing-error class for this inconsistency.
Timeline
ID reserved
By Linux
Published
- 3 months later
· 3 months later
Record updated
Changes after publication (a new score, a public exploit, EPSS crossing 1, 10 or 50 %, leaving KEV) are kept since November 2026; earlier ones are not known.
Scores
| Scored by | CVSS | Score | Vector |
|---|---|---|---|
| LinuxCNA (assigner) | 3.1 | Critical9.8 | CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H |
| NVDNVD · Modified | 3.1 | Critical9.8 | CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H |
- EPSS (exploitation in 30 days)
- 0.50% · top 57% of all CVEs (14 Nov 2026)
- CISA SSVC
- Exploitation: none · Automatable: yes · Technical impact: total
The list uses the assigner's score when there is one, then CISA's, then NVD's: Critical 9.8.
Affected products
- affected 8b6a361b8c482f22ac99c3273285ff16b23fba91 – < 683f7cfbf514193d63c0efa079f3352bde84c2e0
- affected 8b6a361b8c482f22ac99c3273285ff16b23fba91 – < 4a331582011d9e8089af8aa2a61ec6b4443bb245
- affected 8b6a361b8c482f22ac99c3273285ff16b23fba91 – < 33a8b5e971e294ec2a7b74211c545e09efd8e9ac
- affected 8b6a361b8c482f22ac99c3273285ff16b23fba91 – < 14553be882d9ce91749c9d64041de66e34ad8e70
- affected 8b6a361b8c482f22ac99c3273285ff16b23fba91 – < c7c0c0f4379dedec12d24dbb9dded5d2db7fd9f2
- affected 8b6a361b8c482f22ac99c3273285ff16b23fba91 – < 1012896f4225e8f801ff3c1648023845b66dfb11
- affected 8b6a361b8c482f22ac99c3273285ff16b23fba91 – < 775b4dc9618a99a1fa48b57554041a5dc17e1336
- affected 8b6a361b8c482f22ac99c3273285ff16b23fba91 – < 0ce1bc9e46ecabe84772bb561e373c0d9876d6f2
- affected 5.3
- unaffected < 5.3
- unaffected 5.10.258 – ≤ 5.10.*
- unaffected 5.15.209 – ≤ 5.15.*
- unaffected 6.1.175 – ≤ 6.1.*
- unaffected 6.6.142 – ≤ 6.6.*
- unaffected 6.12.92 – ≤ 6.12.*
- unaffected 6.18.34 – ≤ 6.18.*
- unaffected 7.0.11 – ≤ 7.0.*
- unaffected 7.1 – ≤ *
References
References8
- https://git.kernel.org/stable/c/683f7cfbf514193d63c0efa079f3352bde84c2e0 (opens in a new tab)
- https://git.kernel.org/stable/c/4a331582011d9e8089af8aa2a61ec6b4443bb245 (opens in a new tab)
- https://git.kernel.org/stable/c/33a8b5e971e294ec2a7b74211c545e09efd8e9ac (opens in a new tab)
- https://git.kernel.org/stable/c/14553be882d9ce91749c9d64041de66e34ad8e70 (opens in a new tab)
- https://git.kernel.org/stable/c/c7c0c0f4379dedec12d24dbb9dded5d2db7fd9f2 (opens in a new tab)
- https://git.kernel.org/stable/c/1012896f4225e8f801ff3c1648023845b66dfb11 (opens in a new tab)
- https://git.kernel.org/stable/c/775b4dc9618a99a1fa48b57554041a5dc17e1336 (opens in a new tab)
- https://git.kernel.org/stable/c/0ce1bc9e46ecabe84772bb561e373c0d9876d6f2 (opens in a new tab)
Sources
The same CVE in the primary databases and aggregators, to check against.
- CVE.org record (opens in a new tab)
- CVE List JSON (GitHub) (opens in a new tab)
- NVD (opens in a new tab)
- FIRST EPSS (opens in a new tab)
- EUVD EUVD-2026-45787 (opens in a new tab)
- OSV.dev (opens in a new tab)
- GitHub Advisories (opens in a new tab)
- CIRCL Vulnerability-Lookup (opens in a new tab)
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[](https://cveledger.app/cve/CVE-2026-64102)Record last updated .