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Fencer Vulns
high 7.8

CVE-2021-47334 json

misc/libmasm/module: Fix two use after free in ibmasm_init_one

published 2024-05-21 2 y ago modified 2026-06-17 4 mo ago also EUVD-2021-34339

cvss
7.8
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:

misc/libmasm/module: Fix two use after free in ibmasm_init_one

In ibmasm_init_one, it calls ibmasm_init_remote_input_dev(). Inside ibmasm_init_remote_input_dev, mouse_dev and keybd_dev are allocated by input_allocate_device(), and assigned to sp->remote.mouse_dev and sp->remote.keybd_dev respectively.

In the err_free_devices error branch of ibmasm_init_one, mouse_dev and keybd_dev are freed by input_free_device(), and return error. Then the execution runs into error_send_message error branch of ibmasm_init_one, where ibmasm_free_remote_input_dev(sp) is called to unregister the freed sp->remote.mouse_dev and sp->remote.keybd_dev.

My patch add a "error_init_remote" label to handle the error of ibmasm_init_remote_input_dev(), to avoid the uaf bugs.

Patch / fix

  • Linux Linux 4.4.276, 4.9.276, 4.14.240, 4.19.198, 5.4.134, 5.10.52, 5.12.19, 5.13.4, 5.14
  • linux Debian 14, Debian 13, Debian 12 5.14.6-1

debian advisories DEBIAN-CVE-2021-47334

  • linux Ubuntu 18.04 LTS 4.15.0-156.163
  • linux Ubuntu 20.04 LTS 5.4.0-88.99
  • linux-aws Ubuntu 18.04 LTS 4.15.0-1111.118
  • 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 4.15.0-1099.101
  • linux-kvm Ubuntu 20.04 LTS 5.4.0-1047.49

ubuntu advisories UBUNTU-CVE-2021-47334

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-64kb SLES 15 SP3-LTSS, SLE High Performance Computing 15 SP3-LTSS, Enterprise Storage 7.1 5.3.18-150300.59.164.1
  • kernel-syms SLES for SAP 15 SP3, SLES 15 SP3-LTSS, SLE High Performance Computing 15 SP3-LTSS +1 more 5.3.18-150300.59.164.1
  • kernel-source SLES for SAP 15 SP3, SLES 15 SP3-LTSS, SLE High Performance Computing 15 SP3-LTSS +1 more 5.3.18-150300.59.164.1
  • kernel-default SLES for SAP 15 SP3, SLES 15 SP3-LTSS, SLE Micro 5.2 +5 more 5.3.18-150300.59.164.1
  • kernel-preempt SLES for SAP 15 SP3, SLES 15 SP3-LTSS, SLE High Performance Computing 15 SP3-LTSS +1 more 5.3.18-150300.59.164.1
  • kernel-obs-build SLES for SAP 15 SP3, SLES 15 SP3-LTSS, SLE High Performance Computing 15 SP3-LTSS +1 more 5.3.18-150300.59.164.1
  • kernel-default-base SLES for SAP 15 SP3, SLES 15 SP3-LTSS, SLE Micro 5.2 +3 more 5.3.18-150300.59.164.1.150300.18.96.1
  • kernel-syms SLES for SAP 12 SP5, SLES 12 SP5 4.12.14-122.219.1

suse advisories SUSE-SU-2024:2185-1SUSE-SU-2024:2184-1SUSE-SU-2024:2183-1SUSE-SU-2024:2010-1SUSE-SU-2024:1983-1SUSE-SU-2024:1979-1

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-2021-47334 updated cvss 5.6

kernel: misc/libmasm/module: Fix two use after free in ibmasm_init_one

  • 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: 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

0.28% chance of exploitation in the next 30 days, higher than 20% of all scored CVEs (FIRST EPSS, 2026-11-08).

CVSS scores

assigned by version score vector
NVD 3.1 7.8 CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/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.