Skip to content
Fencer Vulns
high 8.3

CVE-2021-22555 kev in the critical feed json

Heap Out-Of-Bounds Write in Netfilter IP6T_SO_SET_REPLACE

published 2021-07-07 5 y ago modified 2026-10-13 26 d ago also EUVD-2021-9696

cvss
8.3
version 3.1, CNA
cisa kev
Exploited
added 2025-10-06
epss
78.7%
EPSS 78.7% chance of exploitation in 30 days, percentile 99.5%
public exploits
2
Metasploit, Exploit-DB

Summary

A heap out-of-bounds write affecting Linux since v2.6.19-rc1 was discovered in net/netfilter/x_tables.c. This allows an attacker to gain privileges or cause a DoS (via heap memory corruption) through user name space

Patch / fix

cisa required action Apply mitigations per vendor instructions, follow applicable BOD 22-01 guidance for cloud services, or discontinue use of the product if mitigations are unavailable.

  • linux linux_kernel 4.4.267, 4.9.267, 4.14.231, 4.19.188, 5.4.113, 5.10.31, 5.12
  • linux Debian 14, Debian 13, Debian 12 5.10.38-1

debian advisories DEBIAN-CVE-2021-22555

  • linux Ubuntu 18.04 LTS 4.15.0-144.148
  • linux Ubuntu 20.04 LTS 5.4.0-74.83
  • linux-aws Ubuntu 18.04 LTS 4.15.0-1103.110
  • linux-aws Ubuntu 20.04 LTS 5.4.0-1049.51
  • linux-gcp Ubuntu 20.04 LTS 5.4.0-1044.47
  • linux-gke Ubuntu 20.04 LTS 5.4.0-1044.46
  • linux-kvm Ubuntu 18.04 LTS 4.15.0-1092.94
  • linux-kvm Ubuntu 20.04 LTS 5.4.0-1040.41

ubuntu advisories UBUNTU-CVE-2021-22555

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

  • redhat-virtualization-host rhev hypervisor 4.4 4.4.7-20210804.0.el8_4
  • redhat-virtualization-host-image-update rhev hypervisor 4.4 4.4.7-20210804.0.el8_4
  • kernel RHEL 7 3.10.0-1160.41.1.el7
  • perf RHEL 7 3.10.0-1160.41.1.el7
  • bpftool RHEL 7 3.10.0-1160.41.1.el7
  • python-perf RHEL 7 3.10.0-1160.41.1.el7
  • kernel-kdump RHEL 7 3.10.0-1160.41.1.el7
  • kernel-tools RHEL 7 3.10.0-1160.41.1.el7

red hat advisories RHSA-2025:17733RHSA-2021:3725RHSA-2021:3814RHSA-2021:3812RHSA-2021:3235RHSA-2021:3327

  • kernel-rt SLE Real Time 12 SP5 4.12.14-10.54.1
  • kernel-syms-rt SLE Real Time 12 SP5 4.12.14-10.54.1
  • kernel-rt_debug SLE Real Time 12 SP5 4.12.14-10.54.1
  • kernel-source-rt SLE Real Time 12 SP5 4.12.14-10.54.1
  • kernel-rt SLE Micro 5.0, Real Time Module 15 SP2 5.3.18-45.3
  • kernel-syms-rt Real Time Module 15 SP2 5.3.18-45.2
  • kernel-rt_debug Real Time Module 15 SP2 5.3.18-45.3
  • kernel-source-rt Real Time Module 15 SP2 5.3.18-45.3

suse advisories SUSE-SU-2021:2643-1SUSE-SU-2021:2599-2SUSE-SU-2021:2599-1SUSE-SU-2021:2584-1SUSE-SU-2021:2577-1SUSE-SU-2021:2560-1

  • kernel-syms openSUSE Leap 15.2 5.3.18-lp152.84.1
  • kernel-obs-qa openSUSE Leap 15.2 5.3.18-lp152.84.1
  • kernel-source openSUSE Leap 15.2 5.3.18-lp152.84.1
  • kernel-default openSUSE Leap 15.2 5.3.18-lp152.84.1
  • kernel-preempt openSUSE Leap 15.2 5.3.18-lp152.84.1
  • kernel-kvmsmall openSUSE Leap 15.2 5.3.18-lp152.84.1
  • kernel-obs-build openSUSE Leap 15.2 5.3.18-lp152.84.1
  • kernel-default-base openSUSE Leap 15.2 5.3.18-lp152.84.1.lp152.8.38.1

opensuse advisories openSUSE-SU-2021:1076-1openSUSE-SU-2021:2427-1openSUSE-SU-2021:2415-1openSUSE-SU-2021:2409-1

  • kernel-rt Rocky Linux 8 4.18.0-305.12.1.rt7.84.el8_4
  • kernel Rocky Linux 8 4.18.0-305.12.1.el8_4

rocky linux advisories RLSA-2021:3088RLSA-2021:3057

  • linux Arch Linux 5.11.15.arch1-2
  • linux-zen Arch Linux 5.11.15.zen1-2
  • linux-hardened Arch Linux 5.11.15.hardened1-1
  • linux-lts Arch Linux 5.10.31-1

arch linux advisories AVG-2161AVG-2162AVG-2163AVG-2164

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-2021-22555 updated cvss 7.8

kernel: out-of-bounds write in xt_compat_target_from_user() in net/netfilter/x_tables.c

  • Red Hat Enterprise Linux 7 perf, kernel, kernel-alt, python-perf, kernel-kdump, kernel-tools, +3 more
    affected: workaround, no fix planned “Out of support scope”
  • Red Hat CodeReady Linux Builder (v. 8) kernel-debuginfo-common-x86_64 4.18.0-305.12.1.el8_4, kernel-debuginfo-common-aarch64 4.18.0-305.12.1.el8_4, kernel-debuginfo-common-ppc64le 4.18.0-305.12.1.el8_4
    fixed: vendor fix RHSA-2021:3057
  • Red Hat CodeReady Linux Builder EUS (v. 8.1) kernel-debuginfo-common-x86_64 4.18.0-147.52.1.el8_1, kernel-debuginfo-common-aarch64 4.18.0-147.52.1.el8_1, kernel-debuginfo-common-ppc64le 4.18.0-147.52.1.el8_1
    fixed: vendor fix RHSA-2021:3173
  • Red Hat CodeReady Linux Builder EUS (v. 8.2) kernel-debuginfo-common-x86_64 4.18.0-193.64.1.el8_2, kernel-debuginfo-common-aarch64 4.18.0-193.64.1.el8_2, kernel-debuginfo-common-ppc64le 4.18.0-193.64.1.el8_2
    fixed: vendor fix RHSA-2021:3363
  • Red Hat Enterprise Linux BaseOS (v. 8) perf 4.18.0-305.12.1.el8_4, kernel 4.18.0-305.12.1.el8_4, bpftool 4.18.0-305.12.1.el8_4, kpatch-patch-4_18_0-305 1-4.el8, kernel-core 4.18.0-305.12.1.el8_4, kernel-tools 4.18.0-305.12.1.el8_4, +19 more
    fixed: vendor fix RHSA-2021:3057
  • Red Hat Enterprise Linux BaseOS EUS (v. 8.1) perf 4.18.0-147.52.1.el8_1, kernel 4.18.0-147.52.1.el8_1, bpftool 4.18.0-147.52.1.el8_1, kernel-core 4.18.0-147.52.1.el8_1, kernel-tools 4.18.0-147.52.1.el8_1, python3-perf 4.18.0-147.52.1.el8_1, +24 more
    fixed: vendor fix RHSA-2021:3173
  • Red Hat Enterprise Linux BaseOS EUS (v. 8.2) perf 4.18.0-193.64.1.el8_2, kernel 4.18.0-193.64.1.el8_2, bpftool 4.18.0-193.64.1.el8_2, kernel-core 4.18.0-193.64.1.el8_2, kernel-tools 4.18.0-193.64.1.el8_2, python3-perf 4.18.0-193.64.1.el8_2, +26 more
    fixed: vendor fix RHSA-2021:3363
  • Red Hat Enterprise Linux Client (v. 7) perf 3.10.0-1160.41.1.el7, kernel 3.10.0-1160.41.1.el7, bpftool 3.10.0-1160.41.1.el7, python-perf 3.10.0-1160.41.1.el7, kernel-tools 3.10.0-1160.41.1.el7, kernel-tools-libs 3.10.0-1160.41.1.el7, +2 more Red Hat Enterprise Linux Client Optional (v. 7) kernel-debuginfo-common-x86_64 3.10.0-1160.41.1.el7 Red Hat Enterprise Linux ComputeNode Optional (v. 7) kernel-debuginfo-common-x86_64 3.10.0-1160.41.1.el7
    fixed: vendor fix RHSA-2021:3327
show 28 more
  • Red Hat Enterprise Linux for Real Time (v. 7) kernel-rt 3.10.0-1160.41.1.rt56.1181.el7, kernel-rt-trace 3.10.0-1160.41.1.rt56.1181.el7, kernel-rt-debuginfo-common-x86_64 3.10.0-1160.41.1.rt56.1181.el7 Red Hat Enterprise Linux for Real Time for NFV (v. 7) kernel-rt 3.10.0-1160.41.1.rt56.1181.el7, kernel-rt-kvm 3.10.0-1160.41.1.rt56.1181.el7, kernel-rt-trace 3.10.0-1160.41.1.rt56.1181.el7, kernel-rt-debug-kvm 3.10.0-1160.41.1.rt56.1181.el7, kernel-rt-trace-kvm 3.10.0-1160.41.1.rt56.1181.el7, kernel-rt-debuginfo-common-x86_64 3.10.0-1160.41.1.rt56.1181.el7
    fixed: vendor fix RHSA-2021:3328
  • Red Hat Enterprise Linux Real Time (v. 8) kernel-rt 4.18.0-305.12.1.rt7.84.el8_4, kernel-rt-core 4.18.0-305.12.1.rt7.84.el8_4, kernel-rt-modules 4.18.0-305.12.1.rt7.84.el8_4, kernel-rt-debug-core 4.18.0-305.12.1.rt7.84.el8_4, kernel-rt-debug-modules 4.18.0-305.12.1.rt7.84.el8_4, kernel-rt-modules-extra 4.18.0-305.12.1.rt7.84.el8_4, +2 more
    fixed: vendor fix RHSA-2021:3088
  • Red Hat Enterprise Linux Real Time EUS (v. 8.2) kernel-rt 4.18.0-193.64.1.rt13.115.el8_2, kernel-rt-core 4.18.0-193.64.1.rt13.115.el8_2, kernel-rt-modules 4.18.0-193.64.1.rt13.115.el8_2, kernel-rt-debug-core 4.18.0-193.64.1.rt13.115.el8_2, kernel-rt-debug-modules 4.18.0-193.64.1.rt13.115.el8_2, kernel-rt-modules-extra 4.18.0-193.64.1.rt13.115.el8_2, +2 more
    fixed: vendor fix RHSA-2021:3375
  • Red Hat Enterprise Linux Real Time for NFV (v. 8) kernel-rt 4.18.0-305.12.1.rt7.84.el8_4, kernel-rt-kvm 4.18.0-305.12.1.rt7.84.el8_4, kernel-rt-core 4.18.0-305.12.1.rt7.84.el8_4, kernel-rt-modules 4.18.0-305.12.1.rt7.84.el8_4, kernel-rt-debug-kvm 4.18.0-305.12.1.rt7.84.el8_4, kernel-rt-debug-core 4.18.0-305.12.1.rt7.84.el8_4, +4 more
    fixed: vendor fix RHSA-2021:3088
  • Red Hat Enterprise Linux Real Time for NFV EUS (v. 8.2) kernel-rt 4.18.0-193.64.1.rt13.115.el8_2, kernel-rt-kvm 4.18.0-193.64.1.rt13.115.el8_2, kernel-rt-core 4.18.0-193.64.1.rt13.115.el8_2, kernel-rt-modules 4.18.0-193.64.1.rt13.115.el8_2, kernel-rt-debug-kvm 4.18.0-193.64.1.rt13.115.el8_2, kernel-rt-debug-core 4.18.0-193.64.1.rt13.115.el8_2, +4 more
    fixed: vendor fix RHSA-2021:3375
  • Red Hat Enterprise Linux Server -EXTENSION(v. 6 ELS-EXTENSION) perf 2.6.32-754.58.1.el6, kernel 2.6.32-754.58.1.el6, kernel-kdump 2.6.32-754.58.1.el6, kernel-firmware 2.6.32-754.58.1.el6, kernel-abi-whitelists 2.6.32-754.58.1.el6, kernel-debuginfo-common-i686 2.6.32-754.58.1.el6, +2 more
    fixed: vendor fix RHSA-2025:17733
  • Red Hat Enterprise Linux Server (v. 7) perf 3.10.0-1160.41.1.el7, kernel 3.10.0-1160.41.1.el7, bpftool 3.10.0-1160.41.1.el7, kpatch-patch-3_10_0-1160 1-8.el7, python-perf 3.10.0-1160.41.1.el7, kernel-kdump 3.10.0-1160.41.1.el7, +18 more
    fixed: vendor fix RHSA-2021:3327
  • Red Hat Enterprise Linux Server AUS (v. 7.2) perf 3.10.0-327.100.1.el7, kernel 3.10.0-327.100.1.el7, python-perf 3.10.0-327.100.1.el7, kernel-tools 3.10.0-327.100.1.el7, kernel-tools-libs 3.10.0-327.100.1.el7, kernel-abi-whitelists 3.10.0-327.100.1.el7, +1 more
    fixed: vendor fix RHSA-2021:3399
  • Red Hat Enterprise Linux Server AUS (v. 7.3) perf 3.10.0-514.92.1.el7, kernel 3.10.0-514.92.1.el7, python-perf 3.10.0-514.92.1.el7, kernel-tools 3.10.0-514.92.1.el7, kernel-tools-libs 3.10.0-514.92.1.el7, kernel-abi-whitelists 3.10.0-514.92.1.el7, +1 more
    fixed: vendor fix RHSA-2021:3321
  • Red Hat Enterprise Linux Server AUS (v. 7.4) perf 3.10.0-693.94.1.el7, kernel 3.10.0-693.94.1.el7, python-perf 3.10.0-693.94.1.el7, kernel-tools 3.10.0-693.94.1.el7, kernel-tools-libs 3.10.0-693.94.1.el7, kernel-abi-whitelists 3.10.0-693.94.1.el7, +1 more
    fixed: vendor fix RHSA-2021:3725
  • Red Hat Enterprise Linux Server AUS (v. 7.6) perf 3.10.0-957.84.1.el7, kernel 3.10.0-957.84.1.el7, bpftool 3.10.0-957.84.1.el7, python-perf 3.10.0-957.84.1.el7, kernel-tools 3.10.0-957.84.1.el7, kernel-tools-libs 3.10.0-957.84.1.el7, +2 more
    fixed: vendor fix RHSA-2021:3812
  • Red Hat Enterprise Linux Server AUS (v. 7.7) perf 3.10.0-1062.56.1.el7, kernel 3.10.0-1062.56.1.el7, bpftool 3.10.0-1062.56.1.el7, python-perf 3.10.0-1062.56.1.el7, kernel-tools 3.10.0-1062.56.1.el7, kernel-tools-libs 3.10.0-1062.56.1.el7, +2 more
    fixed: vendor fix RHSA-2021:3522
  • Red Hat Enterprise Linux Server E4S (v. 7.6) perf 3.10.0-957.84.1.el7, kernel 3.10.0-957.84.1.el7, python-perf 3.10.0-957.84.1.el7, kernel-tools 3.10.0-957.84.1.el7, kpatch-patch-3_10_0-957_61_1 1-6.el7, kpatch-patch-3_10_0-957_61_2 1-6.el7, +13 more
    fixed: vendor fix RHSA-2021:3812
  • Red Hat Enterprise Linux Server E4S (v. 7.7) perf 3.10.0-1062.56.1.el7, kernel 3.10.0-1062.56.1.el7, bpftool 3.10.0-1062.56.1.el7, python-perf 3.10.0-1062.56.1.el7, kernel-tools 3.10.0-1062.56.1.el7, kpatch-patch-3_10_0-1062_36_1 1-5.el7, +13 more
    fixed: vendor fix RHSA-2021:3522
  • Red Hat Enterprise Linux Server Optional -EXTENSION (v. 6 ELS -EXTENSION) python-perf 2.6.32-754.58.1.el6, kernel-debuginfo-common-i686 2.6.32-754.58.1.el6, kernel-debuginfo-common-s390x 2.6.32-754.58.1.el6, kernel-debuginfo-common-x86_64 2.6.32-754.58.1.el6
    fixed: vendor fix RHSA-2025:17733
  • Red Hat Enterprise Linux Server Optional (v. 7) kernel-debuginfo-common-ppc64 3.10.0-1160.41.1.el7, kernel-debuginfo-common-x86_64 3.10.0-1160.41.1.el7, kernel-debuginfo-common-ppc64le 3.10.0-1160.41.1.el7
    fixed: vendor fix RHSA-2021:3327
  • Red Hat Enterprise Linux Server Optional AUS (v. 7.2) kernel-debuginfo-common-x86_64 3.10.0-327.100.1.el7
    fixed: vendor fix RHSA-2021:3399
  • Red Hat Enterprise Linux Server Optional AUS (v. 7.3) kernel-debuginfo-common-x86_64 3.10.0-514.92.1.el7
    fixed: vendor fix RHSA-2021:3321
  • Red Hat Enterprise Linux Server Optional AUS (v. 7.4) kernel-debuginfo-common-x86_64 3.10.0-693.94.1.el7
    fixed: vendor fix RHSA-2021:3725
  • Red Hat Enterprise Linux Server Optional AUS (v. 7.6) kernel-debuginfo-common-x86_64 3.10.0-957.84.1.el7
    fixed: vendor fix RHSA-2021:3812
  • Red Hat Enterprise Linux Server Optional AUS (v. 7.7) kernel-debuginfo-common-x86_64 3.10.0-1062.56.1.el7
    fixed: vendor fix RHSA-2021:3522
  • Red Hat Enterprise Linux Server Optional E4S (v. 7.6) kernel-debuginfo-common-x86_64 3.10.0-957.84.1.el7, kernel-debuginfo-common-ppc64le 3.10.0-957.84.1.el7
    fixed: vendor fix RHSA-2021:3812
  • Red Hat Enterprise Linux Server Optional E4S (v. 7.7) kernel-debuginfo-common-x86_64 3.10.0-1062.56.1.el7, kernel-debuginfo-common-ppc64le 3.10.0-1062.56.1.el7
    fixed: vendor fix RHSA-2021:3522
  • Red Hat Enterprise Linux Server Optional TUS (v. 7.6) kernel-debuginfo-common-x86_64 3.10.0-957.84.1.el7
    fixed: vendor fix RHSA-2021:3812
  • Red Hat Enterprise Linux Server Optional TUS (v. 7.7) kernel-debuginfo-common-x86_64 3.10.0-1062.56.1.el7
    fixed: vendor fix RHSA-2021:3522
  • Red Hat Enterprise Linux Server TUS (v. 7.6) perf 3.10.0-957.84.1.el7, kernel 3.10.0-957.84.1.el7, bpftool 3.10.0-957.84.1.el7, python-perf 3.10.0-957.84.1.el7, kernel-tools 3.10.0-957.84.1.el7, kernel-tools-libs 3.10.0-957.84.1.el7, +2 more
    fixed: vendor fix RHSA-2021:3812
  • Red Hat Enterprise Linux Server TUS (v. 7.7) perf 3.10.0-1062.56.1.el7, kernel 3.10.0-1062.56.1.el7, bpftool 3.10.0-1062.56.1.el7, python-perf 3.10.0-1062.56.1.el7, kernel-tools 3.10.0-1062.56.1.el7, kernel-tools-libs 3.10.0-1062.56.1.el7, +2 more
    fixed: vendor fix RHSA-2021:3522
  • Red Hat Enterprise Linux Workstation (v. 7) perf 3.10.0-1160.41.1.el7, kernel 3.10.0-1160.41.1.el7, bpftool 3.10.0-1160.41.1.el7, python-perf 3.10.0-1160.41.1.el7, kernel-tools 3.10.0-1160.41.1.el7, kernel-tools-libs 3.10.0-1160.41.1.el7, +2 more Red Hat Enterprise Linux Workstation Optional (v. 7) kernel-debuginfo-common-x86_64 3.10.0-1160.41.1.el7
    fixed: vendor fix RHSA-2021:3327

3 more fixed, 3 more not affected in the full advisory

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

Timeline

  1. First public exploit (Metasploit exploit/linux/local/netfilter_xtables_heap_oob_write_priv_esc)
  2. Published
  3. CISA SSVC: exploitation active
  4. Added to CISA KEV
  5. CISA patch deadline

Known exploited

Added
13 mo ago
Patch by
2025-10-27 (12 mo ago)
Ransomware
Not known
Required action
Apply mitigations per vendor instructions, follow applicable BOD 22-01 guidance for cloud services, or discontinue use of the product if mitigations are unavailable.
Vendor, product
Linux, Kernel
CISA name
Linux Kernel Heap Out-of-Bounds Write Vulnerability

CISA SSVC

Exploitation
Active, exploited in the wild
Automatable
no
Technical impact
total
Assessed
13 mo ago

Exploit prediction

78.68% chance of exploitation in the next 30 days, higher than 99.5% of all scored CVEs (FIRST EPSS, 2026-11-08).

Exploits and checks

  • Metasploit exploit/linux/local/netfilter_xtables_heap_oob_write_priv_esc Netfilter x_tables Heap OOB Write Privilege Escalation metasploit exploit, great rank, 2021-07-07
  • EDB-50135 Linux Kernel 2.6.19 < 5.9 - 'Netfilter Local Privilege Escalation local, 2021-07-15
  • github.com https://github.com/google/security-research/security/advisories/GHSA-xxx5-8mvq-3528 referenced PoC, tagged "exploit" by a source, unverified
  • packetstormsecurity.com http://packetstormsecurity.com/files/163878/Kernel-Live-Patch-Security-Notice-LSN-0080-1.html referenced PoC, tagged "exploit" by a source, unverified
  • packetstormsecurity.com http://packetstormsecurity.com/files/164155/Kernel-Live-Patch-Security-Notice-LSN-0081-1.html referenced PoC, tagged "exploit" by a source, unverified
  • packetstormsecurity.com http://packetstormsecurity.com/files/164437/Netfilter-x_tables-Heap-Out-Of-Bounds-Write-Privilege-Escalation.html referenced PoC, tagged "exploit" by a source, unverified
  • packetstormsecurity.com http://packetstormsecurity.com/files/165477/Kernel-Live-Patch-Security-Notice-LSN-0083-1.html referenced PoC, tagged "exploit" by a source, unverified

CVSS scores

assigned by version score vector
CNA 3.1 8.3 CVSS:3.1/AV:A/AC:H/PR:N/UI:N/S:C/C:H/I:H/A:H
NVD 3.1 7.8 CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
NVD 2.0 4.6 AV:L/AC:L/Au:N/C:P/I:P/A:P

Affected products

  • n/a Linux Kernel

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.