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Fencer Vulns
critical 9.8

CVE-2026-64102 in the critical feed json

RDMA/siw: Reject MPA FPDU length underflow before signed receive math

published 2026-07-19 3 mo ago modified 2026-10-19 20 d ago also EUVD-2026-45787

cvss
9.8
version 3.1, CNA
cisa kev
Not listed
not in CISA's catalog
epss
0.5%
EPSS 0.5% chance of exploitation in 30 days, percentile 43%
public exploits
0
none known

Summary

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.

Patch / fix

  • Linux Linux 5.10.258, 5.15.209, 6.1.175, 6.6.142, 6.12.92, 6.18.34, 7.0.11, 7.1
  • linux Debian 12 6.1.176-1
  • linux Debian 13 6.12.94-1
  • linux Debian 14 7.0.12-1

debian advisories DEBIAN-CVE-2026-64102

  • linux Ubuntu 22.04 LTS 5.15.0-186.196
  • linux Ubuntu 24.04 LTS 6.8.0-139.139
  • linux Ubuntu 26.04 LTS 7.0.0-28.28
  • linux-aws Ubuntu 22.04 LTS 5.15.0-1112.119
  • linux-aws Ubuntu 24.04 LTS 6.8.0-1064.67
  • linux-aws Ubuntu 26.04 LTS 7.0.0-1009.9
  • linux-gcp Ubuntu 22.04 LTS 5.15.0-1112.122
  • linux-gcp Ubuntu 24.04 LTS 6.8.0-1067.75

ubuntu advisories UBUNTU-CVE-2026-64102

Ubuntu security data © Canonical Ltd., from https://github.com/canonical/ubuntu-security-notices via OSV; changed: normalised to fixed package versions per release. CC BY-SA 4.0

  • kernel RHEL 8 4.18.0-553.170.1.el8_10
  • perf RHEL 8 4.18.0-553.170.1.el8_10
  • bpftool RHEL 8 4.18.0-553.170.1.el8_10
  • kernel-core RHEL 8 4.18.0-553.170.1.el8_10
  • kernel-tools RHEL 8 4.18.0-553.170.1.el8_10
  • python3-perf RHEL 8 4.18.0-553.170.1.el8_10
  • kernel-modules RHEL 8 4.18.0-553.170.1.el8_10
  • kernel-zfcpdump RHEL 8 4.18.0-553.170.1.el8_10

red hat advisories RHSA-2026:74133RHSA-2026:74132RHSA-2026:72623

  • kernel-64kb SLE Module for Basesystem 15 SP7 6.4.0-150700.53.81.1
  • kernel-syms SLE Module for Development Tools 15 SP7 6.4.0-150700.53.81.1
  • kernel-azure SLE Module for Public Cloud 15 SP7 6.4.0-150700.53.81.1
  • kernel-source SLE Module for Development Tools 15 SP7, SLE Module for Basesystem 15 SP7 6.4.0-150700.53.81.1
  • kernel-default SLE Workstation Extension 15 SP7, SLE Module for Legacy 15 SP7, SLE Module for Basesystem 15 SP7 +2 more 6.4.0-150700.53.81.1
  • kernel-zfcpdump SLE Module for Basesystem 15 SP7 6.4.0-150700.53.81.1
  • kernel-obs-build SLE Module for Development Tools 15 SP7 6.4.0-150700.53.81.1
  • kernel-default-base SLE Module for Basesystem 15 SP7 6.4.0-150700.53.81.1.150700.17.45.1

suse advisories SUSE-SU-2026:4254-1SUSE-SU-2026:23887-1SUSE-SU-2026:23902-1SUSE-SU-2026:23897-1SUSE-SU-2026:23881-1SUSE-SU-2026:4120-1

  • kernel-rt openSUSE Leap 16.0 6.12.0-160000.38.1
  • dtb-aarch64 openSUSE Leap 16.0 6.12.0-160000.38.1
  • kernel-64kb openSUSE Leap 16.0 6.12.0-160000.38.1
  • kernel-syms openSUSE Leap 16.0 6.12.0-160000.38.1
  • kernel-azure openSUSE Leap 16.0 6.12.0-160000.38.1
  • kernel-obs-qa openSUSE Leap 16.0 6.12.0-160000.38.1
  • kernel-source openSUSE Leap 16.0 6.12.0-160000.38.1
  • kernel-default openSUSE Leap 16.0 6.12.0-160000.38.1

opensuse advisories openSUSE-SU-2026:21910-1

  • kernel-rt AlmaLinux 8 4.18.0-553.170.1.rt7.511.el8_10
  • kernel-rt-core AlmaLinux 8 4.18.0-553.170.1.rt7.511.el8_10
  • kernel-rt-modules AlmaLinux 8 4.18.0-553.170.1.rt7.511.el8_10
  • kernel-rt-debug-core AlmaLinux 8 4.18.0-553.170.1.rt7.511.el8_10
  • kernel-rt-debug-modules AlmaLinux 8 4.18.0-553.170.1.rt7.511.el8_10
  • kernel-rt-modules-extra AlmaLinux 8 4.18.0-553.170.1.rt7.511.el8_10
  • kernel-rt-debug-modules-extra AlmaLinux 8 4.18.0-553.170.1.rt7.511.el8_10
  • kernel AlmaLinux 8 4.18.0-553.170.1.el8_10

almalinux advisories ALSA-2026:74132ALSA-2026:74133ALSA-2026:72623

  • kernel-rt Rocky Linux 8 4.18.0-553.170.1.rt7.511.el8_10
  • kernel Rocky Linux 8 4.18.0-553.170.1.el8_10
  • kernel Rocky Linux 9 5.14.0-687.53.1.el9_8

rocky linux advisories RLSA-2026:74132RLSA-2026:74133RLSA-2026:72623

Vendor advisories

What the vendors themselves say about their products: affected, fixed or not affected, and what to do.

red hat product security vex CVE-2026-64102 updated cvss 7.0

kernel: RDMA/siw: Reject MPA FPDU length underflow before signed receive math

  • Red Hat Enterprise Linux 9 kernel-rt, kernel-rt-kvm, kernel-rt-core, kernel-rt-modules, kernel-rt-debug-kvm, kernel-rt-debug-core, +12 more
    affected: no fix available
  • Red Hat Enterprise Linux AppStream (v. 9) rv 5.14.0-687.53.1.el9_8, perf 5.14.0-687.53.1.el9_8, rtla 5.14.0-687.53.1.el9_8, python3-perf 5.14.0-687.53.1.el9_8, kernel-devel-matched 5.14.0-687.53.1.el9_8, kernel-64k-devel-matched 5.14.0-687.53.1.el9_8, +7 more
    fixed: vendor fix RHSA-2026:72623
  • Red Hat Enterprise Linux BaseOS (v. 8) perf 4.18.0-553.170.1.el8_10, kernel 4.18.0-553.170.1.el8_10, bpftool 4.18.0-553.170.1.el8_10, kernel-core 4.18.0-553.170.1.el8_10, kernel-tools 4.18.0-553.170.1.el8_10, python3-perf 4.18.0-553.170.1.el8_10, +15 more
    fixed: vendor fix RHSA-2026:74133
  • Red Hat Enterprise Linux BaseOS (v. 9) kernel 5.14.0-687.53.1.el9_8, kernel-64k 5.14.0-687.53.1.el9_8, kernel-core 5.14.0-687.53.1.el9_8, kernel-tools 5.14.0-687.53.1.el9_8, kernel-modules 5.14.0-687.53.1.el9_8, kernel-64k-core 5.14.0-687.53.1.el9_8, +27 more Red Hat Enterprise Linux CodeReady Linux Builder (v. 9) libperf 5.14.0-687.53.1.el9_8, kernel-debuginfo-common-s390x 5.14.0-687.53.1.el9_8, kernel-debuginfo-common-x86_64 5.14.0-687.53.1.el9_8, kernel-debuginfo-common-aarch64 5.14.0-687.53.1.el9_8, kernel-debuginfo-common-ppc64le 5.14.0-687.53.1.el9_8
    fixed: vendor fix RHSA-2026:72623
  • Red Hat Enterprise Linux CRB (v. 8) kernel-debuginfo-common-x86_64 4.18.0-553.170.1.el8_10, kernel-debuginfo-common-aarch64 4.18.0-553.170.1.el8_10, kernel-debuginfo-common-ppc64le 4.18.0-553.170.1.el8_10
    fixed: vendor fix RHSA-2026:74133
  • Red Hat Enterprise Linux NFV (v. 8) kernel-rt 4.18.0-553.170.1.rt7.511.el8_10, kernel-rt-kvm 4.18.0-553.170.1.rt7.511.el8_10, kernel-rt-core 4.18.0-553.170.1.rt7.511.el8_10, kernel-rt-modules 4.18.0-553.170.1.rt7.511.el8_10, kernel-rt-debug-kvm 4.18.0-553.170.1.rt7.511.el8_10, kernel-rt-debug-core 4.18.0-553.170.1.rt7.511.el8_10, +4 more
    fixed: vendor fix RHSA-2026:74132
  • Red Hat Enterprise Linux Real Time (v. 9) kernel-rt 5.14.0-687.53.1.el9_8, kernel-rt-64k 5.14.0-687.53.1.el9_8, kernel-rt-core 5.14.0-687.53.1.el9_8, kernel-rt-modules 5.14.0-687.53.1.el9_8, kernel-rt-64k-core 5.14.0-687.53.1.el9_8, kernel-rt-debug-core 5.14.0-687.53.1.el9_8, +14 more Red Hat Enterprise Linux Real Time for NFV (v. 9) kernel-rt 5.14.0-687.53.1.el9_8, kernel-rt-core 5.14.0-687.53.1.el9_8, kernel-rt-modules 5.14.0-687.53.1.el9_8, kernel-rt-debug-core 5.14.0-687.53.1.el9_8, kernel-rt-modules-core 5.14.0-687.53.1.el9_8, kernel-rt-debug-modules 5.14.0-687.53.1.el9_8, +4 more
    fixed: vendor fix RHSA-2026:72623
  • Red Hat Enterprise Linux RT (v. 8) kernel-rt 4.18.0-553.170.1.rt7.511.el8_10, kernel-rt-core 4.18.0-553.170.1.rt7.511.el8_10, kernel-rt-modules 4.18.0-553.170.1.rt7.511.el8_10, kernel-rt-debug-core 4.18.0-553.170.1.rt7.511.el8_10, kernel-rt-debug-modules 4.18.0-553.170.1.rt7.511.el8_10, kernel-rt-modules-extra 4.18.0-553.170.1.rt7.511.el8_10, +2 more
    fixed: vendor fix RHSA-2026:74132
show 1 more
  • Red Hat Enterprise Linux 6 perf, kernel, python-perf, kernel-kdump, kernel-firmware, kernel-bootwrapper, +1 more Red Hat Enterprise Linux 7 perf, kernel, bpftool, kernel-rt, python-perf, kernel-kdump, +8 more Red Hat Enterprise Linux 10 kernel
    not affected: vulnerable code not present

Red Hat CSAF VEX © Red Hat, Inc., from https://security.access.redhat.com/data/csaf/v2/vex/; changed: reduced to product statuses and remediations. CC BY 4.0 · csaf

CISA SSVC

Exploitation
none
Automatable
yes
Technical impact
total
Assessed
23 d ago

Exploit prediction

0.50% chance of exploitation in the next 30 days, higher than 43% of all scored CVEs (FIRST EPSS, 2026-11-08).

CVSS scores

assigned by version score vector
CNA 3.1 9.8 CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H

Affected products

  • Linux Linux

Classification

Weakness
Technology feeds

References

Sources

Fencer Vulns keeps one entry per vulnerability: the CVE id wins, then GHSA, and records that alias each other are merged, except that two CVEs always keep separate entries. The same data is available as JSON.