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Fencer Vulns
medium 4.4

CVE-2021-39636 json

In do_ipt_get_ctl and do_ipt_set_ctl of ip_tables.c, there is a possible way to leak kernel information due to uninitialized data.

published 2021-12-15 4 y ago modified 2026-06-17 4 mo ago also EUVD-2021-25993

cvss
4.4
version 3.1, NVD
cisa kev
Not listed
not in CISA's catalog
epss
0.2%
EPSS 0.2% chance of exploitation in 30 days, percentile 13%
public exploits
0
none known

Summary

In do_ipt_get_ctl and do_ipt_set_ctl of ip_tables.c, there is a possible way to leak kernel information due to uninitialized data. This could lead to local information disclosure with system execution privileges needed. User interaction is not needed for exploitation.Product: AndroidVersions: Android kernelAndroid ID: A-120612905References: Upstream kernel

Patch / fix

  • linux Debian 14, Debian 13, Debian 12 4.16.5-1

debian advisories DEBIAN-CVE-2021-39636

  • linux Ubuntu 18.04 LTS 4.15.0-24.26
  • linux-aws Ubuntu 18.04 LTS 4.15.0-1011.11
  • linux-gcp Ubuntu 16.04 LTS 4.15.0-1014.14~16.04.1
  • linux-hwe Ubuntu 16.04 LTS 4.15.0-24.26~16.04.1
  • linux-kvm Ubuntu 18.04 LTS 4.15.0-1012.12
  • linux-azure Ubuntu 16.04 LTS 4.15.0-1014.14~16.04.1
  • linux-raspi2 Ubuntu 18.04 LTS 4.15.0-1013.14
  • linux-snapdragon Ubuntu 18.04 LTS 4.15.0-1053.57

ubuntu advisories UBUNTU-CVE-2021-39636

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

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-2021-39636 updated cvss 4.4

kernel: information disclosure due to uninitialized data in do_ipt_get_ctl() and do_ipt_set_ctl() in ip_tables.c

  • 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, +82 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

Exploit prediction

0.23% chance of exploitation in the next 30 days, higher than 13% of all scored CVEs (FIRST EPSS, 2026-11-08).

CVSS scores

assigned by version score vector
NVD 3.1 4.4 CVSS:3.1/AV:L/AC:L/PR:H/UI:N/S:U/C:H/I:N/A:N
NVD 2.0 2.1 AV:L/AC:L/Au:N/C:P/I:N/A:N

Affected products

  • n/a Android

Classification

Weakness

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.