Skip to content
Fencer Intel
medium 5.5

CVE-2021-47294 json

netrom: Decrease sock refcount when sock timers expire

published 2y ago modified 4mo ago also EUVD-2021-34299

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 20%
public exploits
0
none known

Summary

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

netrom: Decrease sock refcount when sock timers expire

Commit 63346650c1a9 ("netrom: switch to sock timer API") switched to use sock timer API. It replaces mod_timer() by sk_reset_timer(), and del_timer() by sk_stop_timer().

Function sk_reset_timer() will increase the refcount of sock if it is called on an inactive timer, hence, in case the timer expires, we need to decrease the refcount ourselves in the handler, otherwise, the sock refcount will be unbalanced and the sock will never be freed.

Patch / fix

  • Linux Linux 3.19, 4.4.277, 4.9.277, 4.14.241, 4.19.199, 4.21, 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-2021-47294

  • linux Ubuntu 18.04 LTS 4.15.0-159.167
  • linux Ubuntu 20.04 LTS 5.4.0-88.99
  • linux-aws Ubuntu 18.04 LTS 4.15.0-1112.119
  • 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 18.04 LTS 4.15.0-1100.102
  • linux-kvm Ubuntu 20.04 LTS 5.4.0-1047.49

ubuntu advisories UBUNTU-CVE-2021-47294

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-syms SLES for SAP 12 SP5, SLES 12 SP5 4.12.14-122.222.1
  • kernel-source SLES for SAP 12 SP5, SLES 12 SP5 4.12.14-122.222.1
  • kernel-default SLES for SAP 12 SP5, SLES 12 SP5, SLE Workstation Extension 12 SP5 +2 more 4.12.14-122.222.1
  • kernel-obs-build SLE Software Development Kit 12 SP5 4.12.14-122.222.1
  • kernel-rt SLE Real Time 12 SP5 4.12.14-10.191.1
  • kernel-syms-rt SLE Real Time 12 SP5 4.12.14-10.191.1
  • kernel-rt_debug SLE Real Time 12 SP5 4.12.14-10.191.1
  • kernel-source-rt SLE Real Time 12 SP5 4.12.14-10.191.1

suse advisories SUSE-SU-2024:2561-1SUSE-SU-2024:2381-1SUSE-SU-2024:2360-1

Is CVE-2021-47294 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.

Check with Fencer

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-2021-47294 updated cvss 5.5

kernel: netrom: Decrease sock refcount when sock timers expire

  • 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 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
2y ago

Exploit prediction

0.28% chance of exploitation in the next 30 days, higher than 20% 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

Affected products

  • Linux Linux

Classification

Weakness
  • CWE-672 Operation on a Resource after Expiration or Release
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.