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Fencer Vulns
high 7.8

CVE-2026-63996 json

ethtool: cmis: require exact CDB reply length

published 2026-07-19 3 mo ago modified 2026-10-19 20 d ago also EUVD-2026-45569

cvss
7.8
version 3.1, CNA
cisa kev
Not listed
not in CISA's catalog
epss
0.1%
EPSS 0.1% chance of exploitation in 30 days, percentile 2%
public exploits
0
none known

Summary

In the Linux kernel, the following vulnerability has been resolved:

ethtool: cmis: require exact CDB reply length

Malicious SFP module could respond with rpl_len longer than what cmis_cdb_process_reply() expected, leading to OOB writes. Malicious HW is a bit theoretical but some modules may just be buggy and/or the reads may occasionally get corrupted, so let's protect the kernel.

The existing check protects from short replies. We need to protect from long ones, too. All callers that pass a non-zero rpl_exp_len cast the reply payload to a fixed-layout struct and read fields at fixed offsets, with no version negotiation or short-reply handling:

- cmis_cdb_validate_password() - cmis_cdb_module_features_get() - cmis_fw_update_fw_mng_features_get()

so let's assume that responses longer than expected do not have to be handled gracefully here. Add a warning message to make the debug easier in case my understanding is wrong...

Note that page_data->length (argument of kmalloc) comes from last arg to ethtool_cmis_page_init() which is rpl_exp_len.

Note2 that AIs also like to point out overflows in args->req.payload itself (which is a fixed-size 120 B buffer, on the stack), but callers should be reading structs defined by the standard, so protecting from requests for more data than max seem like defensive programming.

Patch / fix

  • Linux Linux 6.12.93, 6.18.35, 7.0.12, 7.1
  • linux Debian 13 6.12.94-1
  • linux Debian 14 7.0.12-1

debian advisories DEBIAN-CVE-2026-63996

  • linux Ubuntu 26.04 LTS 7.0.0-28.28
  • linux-aws Ubuntu 26.04 LTS 7.0.0-1009.9
  • linux-gcp Ubuntu 26.04 LTS 7.0.0-1008.8
  • linux-gke Ubuntu 26.04 LTS 7.0.0-1003.4
  • linux-ibm Ubuntu 26.04 LTS 7.0.0-1010.10
  • linux-azure Ubuntu 26.04 LTS 7.0.0-1010.10
  • linux-raspi Ubuntu 26.04 LTS 7.0.0-1015.15
  • linux-riscv Ubuntu 26.04 LTS 7.0.0-28.28.1

ubuntu advisories UBUNTU-CVE-2026-63996

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-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 AlmaLinux 10 6.12.0-211.73.1.el10_2
  • rv AlmaLinux 10 6.12.0-211.73.1.el10_2
  • perf AlmaLinux 10 6.12.0-211.73.1.el10_2
  • rtla AlmaLinux 10 6.12.0-211.73.1.el10_2
  • libperf AlmaLinux 10 6.12.0-211.73.1.el10_2
  • kernel-rt AlmaLinux 10 6.12.0-211.73.1.el10_2
  • kernel-64k AlmaLinux 10 6.12.0-211.73.1.el10_2
  • kernel-core AlmaLinux 10 6.12.0-211.73.1.el10_2

almalinux advisories ALSA-2026:93911ALSA-2026:93930

  • kernel Rocky Linux 10 6.12.0-211.73.1.el10_2
  • kernel Rocky Linux 9 5.14.0-687.65.1.el9_8

rocky linux advisories RLSA-2026:93911RLSA-2026:93930

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-2026-63996 updated cvss 7.8

kernel: ethtool: cmis: require exact CDB reply length

  • Red Hat Enterprise Linux kernel-modules-internal 6.12.0-211.73.1.el10_2
    fixed: vendor fix RHSA-2026:93911
  • Red Hat Enterprise Linux AppStream (v. 9) rv 5.14.0-687.65.1.el9_8, perf 5.14.0-687.65.1.el9_8, rtla 5.14.0-687.65.1.el9_8, python3-perf 5.14.0-687.65.1.el9_8, kernel-devel-matched 5.14.0-687.65.1.el9_8, kernel-64k-devel-matched 5.14.0-687.65.1.el9_8, +7 more
    fixed: vendor fix RHSA-2026:93930
  • Red Hat Enterprise Linux AppStream (v. 10) rv 6.12.0-211.73.1.el10_2, perf 6.12.0-211.73.1.el10_2, rtla 6.12.0-211.73.1.el10_2, python3-perf 6.12.0-211.73.1.el10_2, kernel-devel-matched 6.12.0-211.73.1.el10_2, kernel-64k-devel-matched 6.12.0-211.73.1.el10_2, +7 more
    fixed: vendor fix RHSA-2026:93911
  • Red Hat Enterprise Linux BaseOS (v. 9) kernel 5.14.0-687.65.1.el9_8, kernel-64k 5.14.0-687.65.1.el9_8, kernel-core 5.14.0-687.65.1.el9_8, kernel-tools 5.14.0-687.65.1.el9_8, kernel-modules 5.14.0-687.65.1.el9_8, kernel-64k-core 5.14.0-687.65.1.el9_8, +27 more
    fixed: vendor fix RHSA-2026:93930
  • Red Hat Enterprise Linux BaseOS (v. 10) kernel 6.12.0-211.73.1.el10_2, kernel-64k 6.12.0-211.73.1.el10_2, kernel-core 6.12.0-211.73.1.el10_2, kernel-tools 6.12.0-211.73.1.el10_2, kernel-modules 6.12.0-211.73.1.el10_2, kernel-64k-core 6.12.0-211.73.1.el10_2, +28 more
    fixed: vendor fix RHSA-2026:93911
  • Red Hat Enterprise Linux CodeReady Linux Builder (v. 9) libperf 5.14.0-687.65.1.el9_8, kernel-debuginfo-common-s390x 5.14.0-687.65.1.el9_8, kernel-debuginfo-common-x86_64 5.14.0-687.65.1.el9_8, kernel-debuginfo-common-aarch64 5.14.0-687.65.1.el9_8, kernel-debuginfo-common-ppc64le 5.14.0-687.65.1.el9_8
    fixed: vendor fix RHSA-2026:93930
  • Red Hat Enterprise Linux CodeReady Linux Builder (v. 10) libperf 6.12.0-211.73.1.el10_2, kernel-debuginfo-common-s390x 6.12.0-211.73.1.el10_2, kernel-debuginfo-common-x86_64 6.12.0-211.73.1.el10_2, kernel-debuginfo-common-aarch64 6.12.0-211.73.1.el10_2, kernel-debuginfo-common-ppc64le 6.12.0-211.73.1.el10_2 Red Hat Enterprise Linux Hidden (v. 10) kernel-modules-internal 6.12.0-211.73.1.el10_2, kernel-debuginfo-common-x86_64 6.12.0-211.73.1.el10_2
    fixed: vendor fix RHSA-2026:93911
  • Red Hat Enterprise Linux Real Time (v. 9) kernel-rt 5.14.0-687.65.1.el9_8, kernel-rt-64k 5.14.0-687.65.1.el9_8, kernel-rt-core 5.14.0-687.65.1.el9_8, kernel-rt-modules 5.14.0-687.65.1.el9_8, kernel-rt-64k-core 5.14.0-687.65.1.el9_8, kernel-rt-debug-core 5.14.0-687.65.1.el9_8, +14 more
    fixed: vendor fix RHSA-2026:93930
show 4 more
  • Red Hat Enterprise Linux Real Time (v. 10) kernel-rt 6.12.0-211.73.1.el10_2, kernel-rt-64k 6.12.0-211.73.1.el10_2, kernel-rt-core 6.12.0-211.73.1.el10_2, kernel-rt-modules 6.12.0-211.73.1.el10_2, kernel-rt-64k-core 6.12.0-211.73.1.el10_2, kernel-rt-debug-core 6.12.0-211.73.1.el10_2, +14 more
    fixed: vendor fix RHSA-2026:93911
  • Red Hat Enterprise Linux Real Time for NFV (v. 9) kernel-rt 5.14.0-687.65.1.el9_8, kernel-rt-core 5.14.0-687.65.1.el9_8, kernel-rt-modules 5.14.0-687.65.1.el9_8, kernel-rt-debug-core 5.14.0-687.65.1.el9_8, kernel-rt-modules-core 5.14.0-687.65.1.el9_8, kernel-rt-debug-modules 5.14.0-687.65.1.el9_8, +4 more
    fixed: vendor fix RHSA-2026:93930
  • Red Hat Enterprise Linux Real Time for NFV (v. 10) kernel-rt 6.12.0-211.73.1.el10_2, kernel-rt-core 6.12.0-211.73.1.el10_2, kernel-rt-modules 6.12.0-211.73.1.el10_2, kernel-rt-debug-core 6.12.0-211.73.1.el10_2, kernel-rt-modules-core 6.12.0-211.73.1.el10_2, kernel-rt-debug-modules 6.12.0-211.73.1.el10_2, +4 more
    fixed: vendor fix RHSA-2026:93911
  • 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 8 perf, kernel, bpftool, kernel-rt, kernel-core, kernel-tools, +29 more 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
    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
no
Technical impact
total
Assessed
23 d ago

Exploit prediction

0.13% chance of exploitation in the next 30 days, higher than 2% of all scored CVEs (FIRST EPSS, 2026-11-08).

CVSS scores

assigned by version score vector
CNA 3.1 7.8 CVSS:3.1/AV:L/AC:L/PR:L/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.