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Fencer Vulns
high 7.8

CVE-2021-47291 json

ipv6: fix another slab-out-of-bounds in fib6_nh_flush_exceptions

published 2024-05-21 2 y ago modified 2026-08-05 3 mo ago also EUVD-2021-34296

cvss
7.8
version 3.1, CNA
cisa kev
Not listed
not in CISA's catalog
epss
0.3%
EPSS 0.3% chance of exploitation in 30 days, percentile 16%
public exploits
0
none known

Summary

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

ipv6: fix another slab-out-of-bounds in fib6_nh_flush_exceptions

While running the self-tests on a KASAN enabled kernel, I observed a slab-out-of-bounds splat very similar to the one reported in commit 821bbf79fe46 ("ipv6: Fix KASAN: slab-out-of-bounds Read in fib6_nh_flush_exceptions").

We additionally need to take care of fib6_metrics initialization failure when the caller provides an nh.

The fix is similar, explicitly free the route instead of calling fib6_info_release on a half-initialized object.

Patch / fix

  • Linux Linux 5.4.136, 5.10.54, 5.13.6, 5.14
  • linux Debian 14, Debian 13, Debian 12 5.14.6-1

debian advisories DEBIAN-CVE-2021-47291

  • linux Ubuntu 20.04 LTS 5.4.0-88.99
  • linux-aws Ubuntu 20.04 LTS 5.4.0-1057.60
  • linux-gcp Ubuntu 20.04 LTS 5.4.0-1053.57
  • linux-ibm Ubuntu 20.04 LTS 5.4.0-1005.6
  • linux-kvm Ubuntu 20.04 LTS 5.4.0-1047.49
  • linux-azure Ubuntu 20.04 LTS 5.4.0-1059.62
  • linux-gkeop Ubuntu 20.04 LTS 5.4.0-1024.25
  • linux-raspi Ubuntu 20.04 LTS 5.4.0-1044.48

ubuntu advisories UBUNTU-CVE-2021-47291

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-livepatch-SLE15-SP3_Update_42 SLE Live Patching 15 SP3 12-150300.7.6.1
  • kernel-livepatch-SLE15-SP3_Update_46 SLE Live Patching 15 SP3 6-150300.7.6.1
  • kernel-livepatch-SLE15-SP3_Update_43 SLE Live Patching 15 SP3 11-150300.7.6.1
  • kernel-livepatch-SLE15-SP3_Update_45 SLE Live Patching 15 SP3 7-150300.7.6.1
  • kernel-livepatch-SLE15-SP3_Update_44 SLE Live Patching 15 SP3 10-150300.7.6.1
  • kernel-livepatch-SLE15-SP3_Update_44 SLE Live Patching 15 SP3 9-150300.7.6.1
  • kernel-livepatch-SLE15-SP3_Update_45 SLE Live Patching 15 SP3 6-150300.7.6.1
  • kernel-livepatch-SLE15-SP3_Update_43 SLE Live Patching 15 SP3 10-150300.7.6.1

suse advisories SUSE-SU-2025:0244-1SUSE-SU-2025:0243-1SUSE-SU-2025:0240-1SUSE-SU-2025:0239-1SUSE-SU-2025:0238-1SUSE-SU-2025:0137-1

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-2021-47291 updated cvss 5.5

kernel: ipv6: fix another slab-out-of-bounds in fib6_nh_flush_exceptions

  • 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
    affected: workaround, no fix planned “Out of support scope”
  • Red Hat Enterprise Linux 8 perf, kernel, bpftool, kernel-rt, kernel-core, kernel-tools, +29 more Red Hat Enterprise Linux 9 rv, perf, rtla, kernel, bpftool, libperf, +83 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
partial
Assessed
2 y ago

Exploit prediction

0.25% chance of exploitation in the next 30 days, higher than 16% 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
NVD 3.1 7.1 CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:N/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.