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critical 9.8

CVE-2026-63984 in the critical feed json

ipv6: rpl: fix hdrlen overflow in ipv6_rpl_srh_decompress()

published 3mo ago modified 23d ago also EUVD-2026-45757

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 44%
public exploits
0
none known

Summary

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

ipv6: rpl: fix hdrlen overflow in ipv6_rpl_srh_decompress()

ipv6_rpl_srh_decompress() computes:

outhdr->hdrlen = (((n + 1) * sizeof(struct in6_addr)) >> 3);

hdrlen is __u8. For n >= 127 the result exceeds 255 and silently truncates. With n=127 (cmpri=15, cmpre=15, pad=0, hdrlen=16):

(128 * 16) >> 3 = 256, truncated to 0 as __u8

The caller in ipv6_rpl_srh_rcv() then places the compressed header at buf + ((ohdr->hdrlen + 1) << 3). With hdrlen=0 this is buf + 8, but the decompressed region occupies buf[0..2055] (8-byte header plus 128 full addresses). The compressed header overlaps the decompressed data, and ipv6_rpl_srh_compress() writes into this overlap, corrupting the routing header of the forwarded packet.

The existing guard at exthdrs.c:546 checks (n + 1) > 255, which prevents n+1 from overflowing unsigned char (the segments_left field), but does not prevent the computed hdrlen from overflowing __u8. n=127 passes because 128 <= 255, yet hdrlen=256 does not fit.

Tighten the bound to (n + 1) > 127. This caps n at 126, giving hdrlen = (127 * 16) >> 3 = 254, which fits in __u8. The compressed header then lands at buf + ((254 + 1) << 3) = buf + 2040, exactly past the decompressed region (buf[0..2039]). No overlap. 127 segments is well beyond any realistic RPL deployment.

Patch / fix

  • Linux Linux 5.10.259, 5.15.210, 6.1.176, 6.6.143, 6.12.93, 6.18.35, 7.0.12, 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-2026-63984

  • linux Ubuntu 22.04 LTS 5.15.0-194.204
  • linux Ubuntu 24.04 LTS 6.8.0-142.142
  • linux Ubuntu 26.04 LTS 7.0.0-28.28
  • linux-aws Ubuntu 22.04 LTS 5.15.0-1116.123
  • linux-aws Ubuntu 24.04 LTS 6.8.0-1065.68
  • linux-aws Ubuntu 26.04 LTS 7.0.0-1009.9
  • linux-gcp Ubuntu 22.04 LTS 5.15.0-1117.127
  • linux-gcp Ubuntu 24.04 LTS 6.8.0-1069.77

ubuntu advisories UBUNTU-CVE-2026-63984

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 9 5.14.0-687.55.1.el9_8
  • rv RHEL 9 5.14.0-687.55.1.el9_8
  • perf RHEL 9 5.14.0-687.55.1.el9_8
  • rtla RHEL 9 5.14.0-687.55.1.el9_8
  • libperf RHEL 9 5.14.0-687.55.1.el9_8
  • kernel-rt RHEL 9 5.14.0-687.55.1.el9_8
  • kernel-64k RHEL 9 5.14.0-687.55.1.el9_8
  • kernel-core RHEL 9 5.14.0-687.55.1.el9_8

red hat advisories RHSA-2026:83707RHSA-2026:77219RHSA-2026:76739RHSA-2026:77218

  • kernel-default SLES for SAP 15 SP6, SLES 15 SP6-LTSS, SLE Live Patching 15 SP6 +1 more 6.4.0-150600.23.130.1
  • kernel-rt Linux Micro 6.2 6.12.0-160000.38.1
  • kernel-64kb SLES 16.0, Linux Micro 6.2, SLES for SAP applications 16.0 6.12.0-160000.38.1
  • kernel-source SLES 16.0, Linux Micro 6.2, SLES for SAP applications 16.0 6.12.0-160000.38.1
  • kernel-default SLES 16.0, SLE High Availability Extension 16.0, Linux Micro 6.2 +1 more 6.12.0-160000.38.1
  • kernel-default-base SLES 16.0, Linux Micro 6.2, SLES for SAP applications 16.0 6.12.0-160000.38.1.160000.2.23
  • kernel-syms SLES 16.0, Linux Micro Extras 6.2, SLES for SAP applications 16.0 6.12.0-160000.38.1
  • kernel-azure SLES for SAP applications 16.0, SLES 16.0 6.12.0-160000.38.1

suse advisories SUSE-SU-2026:3602-1SUSE-SU-2026:23887-1SUSE-SU-2026:23902-1SUSE-SU-2026:23897-1SUSE-SU-2026:23881-1SUSE-SU-2026:3595-1

  • 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 6.12.0-211.63.1.el10_2
  • rv AlmaLinux 10 6.12.0-211.63.1.el10_2
  • perf AlmaLinux 10 6.12.0-211.63.1.el10_2
  • rtla AlmaLinux 10 6.12.0-211.63.1.el10_2
  • libperf AlmaLinux 10 6.12.0-211.63.1.el10_2
  • kernel-rt AlmaLinux 10 6.12.0-211.63.1.el10_2
  • kernel-64k AlmaLinux 10 6.12.0-211.63.1.el10_2
  • kernel-core AlmaLinux 10 6.12.0-211.63.1.el10_2

almalinux advisories ALSA-2026:76738

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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-2026-63984 updated cvss 4.8

kernel: ipv6: rpl: fix hdrlen overflow in ipv6_rpl_srh_decompress()

  • Red Hat Enterprise Linux 6 perf, kernel, python-perf, kernel-kdump, kernel-firmware, kernel-bootwrapper, +1 more
    affected: workaround, no fix planned “Out of support scope”
  • 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: workaround, no fix available
  • Red Hat CodeReady Linux Builder EUS (v.9.6) libperf 5.14.0-570.147.1.el9_6, kernel-debuginfo-common-s390x 5.14.0-570.147.1.el9_6, kernel-debuginfo-common-x86_64 5.14.0-570.147.1.el9_6, kernel-debuginfo-common-aarch64 5.14.0-570.147.1.el9_6, kernel-debuginfo-common-ppc64le 5.14.0-570.147.1.el9_6
    fixed: vendor fix RHSA-2026:77219
  • Red Hat Enterprise Linux kernel-modules-internal 6.12.0-211.63.1.el10_2
    fixed: vendor fix RHSA-2026:76738
  • Red Hat Enterprise Linux AppStream (v. 9) rv 5.14.0-687.55.1.el9_8, perf 5.14.0-687.55.1.el9_8, rtla 5.14.0-687.55.1.el9_8, python3-perf 5.14.0-687.55.1.el9_8, kernel-devel-matched 5.14.0-687.55.1.el9_8, kernel-64k-devel-matched 5.14.0-687.55.1.el9_8, +7 more
    fixed: vendor fix RHSA-2026:76739
  • Red Hat Enterprise Linux AppStream (v. 10) rv 6.12.0-211.63.1.el10_2, perf 6.12.0-211.63.1.el10_2, rtla 6.12.0-211.63.1.el10_2, python3-perf 6.12.0-211.63.1.el10_2, kernel-devel-matched 6.12.0-211.63.1.el10_2, kernel-64k-devel-matched 6.12.0-211.63.1.el10_2, +7 more
    fixed: vendor fix RHSA-2026:76738
  • Red Hat Enterprise Linux AppStream E4S (v.9.2) perf 5.14.0-284.200.1.el9_2, rtla 5.14.0-284.200.1.el9_2, kernel-devel-matched 5.14.0-284.200.1.el9_2, kernel-64k-devel-matched 5.14.0-284.200.1.el9_2, kernel-debug-devel-matched 5.14.0-284.200.1.el9_2, kernel-debuginfo-common-s390x 5.14.0-284.200.1.el9_2, +5 more
    fixed: vendor fix RHSA-2026:92993
  • Red Hat Enterprise Linux AppStream E4S (v.9.4) rv 5.14.0-427.154.1.el9_4, perf 5.14.0-427.154.1.el9_4, rtla 5.14.0-427.154.1.el9_4, kernel-devel-matched 5.14.0-427.154.1.el9_4, kernel-64k-devel-matched 5.14.0-427.154.1.el9_4, kernel-debug-devel-matched 5.14.0-427.154.1.el9_4, +6 more
    fixed: vendor fix RHSA-2026:77218
show 25 more
  • Red Hat Enterprise Linux AppStream EUS (v. 10.0) rv 6.12.0-55.111.1.el10_0, perf 6.12.0-55.111.1.el10_0, rtla 6.12.0-55.111.1.el10_0, python3-perf 6.12.0-55.111.1.el10_0, kernel-devel-matched 6.12.0-55.111.1.el10_0, kernel-64k-devel-matched 6.12.0-55.111.1.el10_0, +7 more
    fixed: vendor fix RHSA-2026:83707
  • Red Hat Enterprise Linux AppStream EUS (v.9.6) rv 5.14.0-570.147.1.el9_6, perf 5.14.0-570.147.1.el9_6, rtla 5.14.0-570.147.1.el9_6, python3-perf 5.14.0-570.147.1.el9_6, kernel-devel-matched 5.14.0-570.147.1.el9_6, kernel-64k-devel-matched 5.14.0-570.147.1.el9_6, +7 more
    fixed: vendor fix RHSA-2026:77219
  • Red Hat Enterprise Linux BaseOS (v. 9) kernel 5.14.0-687.55.1.el9_8, kernel-64k 5.14.0-687.55.1.el9_8, kernel-core 5.14.0-687.55.1.el9_8, kernel-tools 5.14.0-687.55.1.el9_8, kernel-modules 5.14.0-687.55.1.el9_8, kernel-64k-core 5.14.0-687.55.1.el9_8, +27 more
    fixed: vendor fix RHSA-2026:76739
  • Red Hat Enterprise Linux BaseOS (v. 10) kernel 6.12.0-211.63.1.el10_2, kernel-64k 6.12.0-211.63.1.el10_2, kernel-core 6.12.0-211.63.1.el10_2, kernel-tools 6.12.0-211.63.1.el10_2, kernel-modules 6.12.0-211.63.1.el10_2, kernel-64k-core 6.12.0-211.63.1.el10_2, +28 more
    fixed: vendor fix RHSA-2026:76738
  • Red Hat Enterprise Linux BaseOS E4S (v.9.2) bpftool 7.0.0-284.200.1.el9_2, kernel 5.14.0-284.200.1.el9_2, kernel-64k 5.14.0-284.200.1.el9_2, kernel-core 5.14.0-284.200.1.el9_2, kernel-tools 5.14.0-284.200.1.el9_2, python3-perf 5.14.0-284.200.1.el9_2, +28 more
    fixed: vendor fix RHSA-2026:92993
  • Red Hat Enterprise Linux BaseOS E4S (v.9.4) bpftool 7.3.0-427.154.1.el9_4, kernel 5.14.0-427.154.1.el9_4, kernel-64k 5.14.0-427.154.1.el9_4, kernel-core 5.14.0-427.154.1.el9_4, kernel-tools 5.14.0-427.154.1.el9_4, python3-perf 5.14.0-427.154.1.el9_4, +28 more
    fixed: vendor fix RHSA-2026:77218
  • Red Hat Enterprise Linux BaseOS EUS (v. 10.0) kernel 6.12.0-55.111.1.el10_0, kernel-64k 6.12.0-55.111.1.el10_0, kernel-core 6.12.0-55.111.1.el10_0, kernel-tools 6.12.0-55.111.1.el10_0, kernel-modules 6.12.0-55.111.1.el10_0, kernel-64k-core 6.12.0-55.111.1.el10_0, +27 more
    fixed: vendor fix RHSA-2026:83707
  • Red Hat Enterprise Linux BaseOS EUS (v.9.6) kernel 5.14.0-570.147.1.el9_6, kernel-64k 5.14.0-570.147.1.el9_6, kernel-core 5.14.0-570.147.1.el9_6, kernel-tools 5.14.0-570.147.1.el9_6, kernel-modules 5.14.0-570.147.1.el9_6, kernel-64k-core 5.14.0-570.147.1.el9_6, +27 more
    fixed: vendor fix RHSA-2026:77219
  • Red Hat Enterprise Linux CodeReady Linux Builder (v. 9) libperf 5.14.0-687.55.1.el9_8, kernel-debuginfo-common-s390x 5.14.0-687.55.1.el9_8, kernel-debuginfo-common-x86_64 5.14.0-687.55.1.el9_8, kernel-debuginfo-common-aarch64 5.14.0-687.55.1.el9_8, kernel-debuginfo-common-ppc64le 5.14.0-687.55.1.el9_8
    fixed: vendor fix RHSA-2026:76739
  • Red Hat Enterprise Linux CodeReady Linux Builder (v. 10) libperf 6.12.0-211.63.1.el10_2, kernel-debuginfo-common-s390x 6.12.0-211.63.1.el10_2, kernel-debuginfo-common-x86_64 6.12.0-211.63.1.el10_2, kernel-debuginfo-common-aarch64 6.12.0-211.63.1.el10_2, kernel-debuginfo-common-ppc64le 6.12.0-211.63.1.el10_2
    fixed: vendor fix RHSA-2026:76738
  • Red Hat Enterprise Linux CodeReady Linux Builder EUS (v. 10.0) libperf 6.12.0-55.111.1.el10_0, kernel-debuginfo-common-s390x 6.12.0-55.111.1.el10_0, kernel-debuginfo-common-x86_64 6.12.0-55.111.1.el10_0, kernel-debuginfo-common-aarch64 6.12.0-55.111.1.el10_0, kernel-debuginfo-common-ppc64le 6.12.0-55.111.1.el10_0
    fixed: vendor fix RHSA-2026:83707
  • Red Hat Enterprise Linux Hidden (v. 10) kernel-modules-internal 6.12.0-211.63.1.el10_2, kernel-debuginfo-common-x86_64 6.12.0-211.63.1.el10_2
    fixed: vendor fix RHSA-2026:76738
  • Red Hat Enterprise Linux Real Time (v. 9) kernel-rt 5.14.0-687.55.1.el9_8, kernel-rt-64k 5.14.0-687.55.1.el9_8, kernel-rt-core 5.14.0-687.55.1.el9_8, kernel-rt-modules 5.14.0-687.55.1.el9_8, kernel-rt-64k-core 5.14.0-687.55.1.el9_8, kernel-rt-debug-core 5.14.0-687.55.1.el9_8, +14 more
    fixed: vendor fix RHSA-2026:76739
  • Red Hat Enterprise Linux Real Time (v. 10) kernel-rt 6.12.0-211.63.1.el10_2, kernel-rt-64k 6.12.0-211.63.1.el10_2, kernel-rt-core 6.12.0-211.63.1.el10_2, kernel-rt-modules 6.12.0-211.63.1.el10_2, kernel-rt-64k-core 6.12.0-211.63.1.el10_2, kernel-rt-debug-core 6.12.0-211.63.1.el10_2, +14 more
    fixed: vendor fix RHSA-2026:76738
  • Red Hat Enterprise Linux Real Time E4S (v.9.2) kernel-rt 5.14.0-284.200.1.rt14.485.el9_2, kernel-rt-core 5.14.0-284.200.1.rt14.485.el9_2, kernel-rt-modules 5.14.0-284.200.1.rt14.485.el9_2, kernel-rt-debug-core 5.14.0-284.200.1.rt14.485.el9_2, kernel-rt-modules-core 5.14.0-284.200.1.rt14.485.el9_2, kernel-rt-debug-modules 5.14.0-284.200.1.rt14.485.el9_2, +4 more
    fixed: vendor fix RHSA-2026:93047
  • Red Hat Enterprise Linux Real Time E4S (v.9.4) kernel-rt 5.14.0-427.154.1.el9_4, kernel-rt-core 5.14.0-427.154.1.el9_4, kernel-rt-modules 5.14.0-427.154.1.el9_4, kernel-rt-debug-core 5.14.0-427.154.1.el9_4, kernel-rt-modules-core 5.14.0-427.154.1.el9_4, kernel-rt-debug-modules 5.14.0-427.154.1.el9_4, +4 more
    fixed: vendor fix RHSA-2026:77218
  • Red Hat Enterprise Linux Real Time EUS (v. 10.0) kernel-rt 6.12.0-55.111.1.el10_0, kernel-rt-64k 6.12.0-55.111.1.el10_0, kernel-rt-core 6.12.0-55.111.1.el10_0, kernel-rt-modules 6.12.0-55.111.1.el10_0, kernel-rt-64k-core 6.12.0-55.111.1.el10_0, kernel-rt-debug-core 6.12.0-55.111.1.el10_0, +14 more
    fixed: vendor fix RHSA-2026:83707
  • Red Hat Enterprise Linux Real Time EUS (v.9.6) kernel-rt 5.14.0-570.147.1.el9_6, kernel-rt-64k 5.14.0-570.147.1.el9_6, kernel-rt-core 5.14.0-570.147.1.el9_6, kernel-rt-modules 5.14.0-570.147.1.el9_6, kernel-rt-64k-core 5.14.0-570.147.1.el9_6, kernel-rt-debug-core 5.14.0-570.147.1.el9_6, +14 more
    fixed: vendor fix RHSA-2026:77219
  • Red Hat Enterprise Linux Real Time for NFV (v. 9) kernel-rt 5.14.0-687.55.1.el9_8, kernel-rt-core 5.14.0-687.55.1.el9_8, kernel-rt-modules 5.14.0-687.55.1.el9_8, kernel-rt-debug-core 5.14.0-687.55.1.el9_8, kernel-rt-modules-core 5.14.0-687.55.1.el9_8, kernel-rt-debug-modules 5.14.0-687.55.1.el9_8, +4 more
    fixed: vendor fix RHSA-2026:76739
  • Red Hat Enterprise Linux Real Time for NFV (v. 10) kernel-rt 6.12.0-211.63.1.el10_2, kernel-rt-core 6.12.0-211.63.1.el10_2, kernel-rt-modules 6.12.0-211.63.1.el10_2, kernel-rt-debug-core 6.12.0-211.63.1.el10_2, kernel-rt-modules-core 6.12.0-211.63.1.el10_2, kernel-rt-debug-modules 6.12.0-211.63.1.el10_2, +4 more
    fixed: vendor fix RHSA-2026:76738
  • Red Hat Enterprise Linux Real Time for NFV E4S (v.9.2) kernel-rt 5.14.0-284.200.1.rt14.485.el9_2, kernel-rt-kvm 5.14.0-284.200.1.rt14.485.el9_2, kernel-rt-core 5.14.0-284.200.1.rt14.485.el9_2, kernel-rt-modules 5.14.0-284.200.1.rt14.485.el9_2, kernel-rt-debug-kvm 5.14.0-284.200.1.rt14.485.el9_2, kernel-rt-debug-core 5.14.0-284.200.1.rt14.485.el9_2, +6 more
    fixed: vendor fix RHSA-2026:93047
  • Red Hat Enterprise Linux Real Time for NFV E4S (v.9.4) kernel-rt 5.14.0-427.154.1.el9_4, kernel-rt-kvm 5.14.0-427.154.1.el9_4, kernel-rt-core 5.14.0-427.154.1.el9_4, kernel-rt-modules 5.14.0-427.154.1.el9_4, kernel-rt-debug-kvm 5.14.0-427.154.1.el9_4, kernel-rt-debug-core 5.14.0-427.154.1.el9_4, +6 more
    fixed: vendor fix RHSA-2026:77218
  • Red Hat Enterprise Linux Real Time for NFV EUS (v. 10.0) kernel-rt 6.12.0-55.111.1.el10_0, kernel-rt-kvm 6.12.0-55.111.1.el10_0, kernel-rt-core 6.12.0-55.111.1.el10_0, kernel-rt-modules 6.12.0-55.111.1.el10_0, kernel-rt-debug-kvm 6.12.0-55.111.1.el10_0, kernel-rt-debug-core 6.12.0-55.111.1.el10_0, +6 more
    fixed: vendor fix RHSA-2026:83707
  • Red Hat Enterprise Linux Real Time for NFV EUS (v.9.6) kernel-rt 5.14.0-570.147.1.el9_6, kernel-rt-kvm 5.14.0-570.147.1.el9_6, kernel-rt-core 5.14.0-570.147.1.el9_6, kernel-rt-modules 5.14.0-570.147.1.el9_6, kernel-rt-debug-kvm 5.14.0-570.147.1.el9_6, kernel-rt-debug-core 5.14.0-570.147.1.el9_6, +6 more
    fixed: vendor fix RHSA-2026:77219
  • 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
    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
26d ago

Exploit prediction

0.51% chance of exploitation in the next 30 days, higher than 44% of all scored CVEs (FIRST EPSS, 2026-11-11).

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
  • CWE-190 Integer Overflow or Wraparound
Technology feeds

References

Sources

Fencer Intel 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.