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Fencer Intel
medium 5.5

CVE-2020-12656 json

gss_mech_free in net/sunrpc/auth_gss/gss_mech_switch.c in the rpcsec_gss_krb5 implementation in the Linux kernel through 5.6.10 lacks certa…

published 6y ago modified 4mo ago also EUVD-2020-4955

cvss
5.5
version 3.1, NVD
cisa kev
Not listed
not in CISA's catalog
epss
0.3%
EPSS 0.3% chance of exploitation in 30 days, percentile 26%
public exploits
0
none known

Summary

gss_mech_free in net/sunrpc/auth_gss/gss_mech_switch.c in the rpcsec_gss_krb5 implementation in the Linux kernel through 5.6.10 lacks certain domain_release calls, leading to a memory leak. Note: This was disputed with the assertion that the issue does not grant any access not already available. It is a problem that on unloading a specific kernel module some memory is leaked, but loading kernel modules is a privileged operation. A user could also write a kernel module to consume any amount of memory they like and load that replicating the effect of this bug

Patch / fix

  • linux Debian 14, Debian 13, Debian 12 5.7.6-1

debian advisories DEBIAN-CVE-2020-12656

  • linux Ubuntu 16.04 LTS 4.4.0-186.216
  • linux Ubuntu 18.04 LTS 4.15.0-115.116
  • linux Ubuntu 20.04 LTS 5.4.0-45.49
  • linux-aws Ubuntu 16.04 LTS 4.4.0-1111.123
  • linux-aws Ubuntu 18.04 LTS 4.15.0-1080.84
  • linux-aws Ubuntu 20.04 LTS 5.4.0-1022.22
  • linux-gcp Ubuntu 16.04 LTS 4.15.0-1081.92~16.04.1
  • linux-gcp Ubuntu 20.04 LTS 5.4.0-1022.22

ubuntu advisories UBUNTU-CVE-2020-12656

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-rt Real Time Module 15 SP1 4.12.14-14.28.1
  • kernel-syms-rt Real Time Module 15 SP1 4.12.14-14.28.1
  • kernel-rt_debug Real Time Module 15 SP1 4.12.14-14.28.1
  • kernel-source-rt Real Time Module 15 SP1 4.12.14-14.28.1
  • kernel-rt SLE Real Time 12 SP5 4.12.14-10.13.1
  • kernel-syms-rt SLE Real Time 12 SP5 4.12.14-10.13.1
  • kernel-rt_debug SLE Real Time 12 SP5 4.12.14-10.13.1
  • kernel-source-rt SLE Real Time 12 SP5 4.12.14-10.13.1

suse advisories SUSE-SU-2020:2487-1SUSE-SU-2020:2478-1SUSE-SU-2020:2156-1SUSE-SU-2020:14442-1SUSE-SU-2020:2105-1SUSE-SU-2020:2027-1

  • kernel-rt openSUSE Leap 15.2 5.3.18-lp152.3.5.1
  • kernel-syms-rt openSUSE Leap 15.2 5.3.18-lp152.3.5.1
  • kernel-rt_debug openSUSE Leap 15.2 5.3.18-lp152.3.5.1
  • kernel-source-rt openSUSE Leap 15.2 5.3.18-lp152.3.5.1
  • kernel-syms openSUSE Leap 15.2 5.3.18-lp152.26.2
  • kernel-obs-qa openSUSE Leap 15.2 5.3.18-lp152.26.2
  • kernel-source openSUSE Leap 15.2 5.3.18-lp152.26.2
  • kernel-default openSUSE Leap 15.2 5.3.18-lp152.26.2

opensuse advisories openSUSE-SU-2021:0242-1openSUSE-SU-2020:0935-1openSUSE-SU-2020:0801-1

Is CVE-2020-12656 in your stack? Fencer shows which of your repositories are affected as soon as an advisory lands, and opens the fix as a pull request.

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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-2020-12656 updated cvss 4.4

kernel: gss_mech_free in net/sunrpc/auth_gss/gss_mech_switch.c in the rpcsec_gss_krb5 implementation lacks certain domain_release calls, leading to a memory leak.

  • Red Hat Enterprise Linux 5 kernel 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 7 perf, kernel, bpftool, kernel-rt, kernel-alt, python-perf, +9 more
    affected: workaround, no fix available “Fix deferred”
  • Red Hat Enterprise Linux 8 perf, kernel, bpftool, kernel-rt, kernel-core, kernel-tools, +29 more
    affected: workaround, no fix available
  • Red Hat Enterprise MRG 2 kernel-rt, mrg-rt-release, kernel-rt-trace, kernel-rt-vanilla, kernel-rt-firmware
    affected: workaround, no fix planned “Out of support scope”

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
2y ago

Exploit prediction

0.33% chance of exploitation in the next 30 days, higher than 26% of all scored CVEs (FIRST EPSS, 2026-11-09).

CVSS scores

assigned by version score vector
NVD 3.1 5.5 CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H
NVD 2.0 2.1 AV:L/AC:L/Au:N/C:N/I:N/A:P

Classification

Weakness
  • CWE-401 Missing Release of Memory after Effective Lifetime
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.