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NVD / CVE Program· CNA Linux

CVE-2021-47334: misc/libmasm/module: Fix two use after free in ibmasm_init_one

Noroxi assessment

Priority: Monitor (action score 31/100)

  • The sources we track (CISA KEV, Exploit-DB, Metasploit, Nuclei, GitHub) show no public exploit code or exploitation in the wild.
  • Probability of exploitation in the next 30 days: 0.27% (FIRST EPSS).
  • Someone with local access to the system can trigger it. A low-privileged account is enough. No user action is required. No special conditions are required; it is repeatable.
  • Fixed version: Linux Linux 1512e7dc5eb08b7d92a12e2bfcd9cb8c4a1ec069, 29ba8e2ba89ee2862a26d91204dd5fe77ceee25a, 38660031e80eaa6cc9370b031c180612f414b00d.
  • Mentioned 1 time in Turkish national cyber security advisories (siberguvenlik.gov.tr).

Low priority for now. Upgrade to Linux Linux 1512e7dc5eb08b7d92a12e2bfcd9cb8c4a1ec069, 29ba8e2ba89ee2862a26d91204dd5fe77ceee25a, 38660031e80eaa6cc9370b031c180612f414b00d or later.

Generated automatically from the record's data: CVSS (NVD and CNA), CISA KEV and SSVC, FIRST EPSS, exploit sources, fixed versions. How we calculate it

Primary sources: NVD · CVE.org · FIRST EPSS

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.

HighCVSS 7.8 · v3.1—No exploit Fix available
Published
May 21, 2024
Updated
Jun 17, 2026
EPSS
0.2% · 20th percentile

Report tools

JSON

Action score

31

Monitor

Low priority for now.

CVSS
31 / 40 · 7.8 / 10
CISA KEV
0 / 30 · Not listed
EPSS
0 / 30 · 0.2%

CISA SSVC decision

Exploitation
none
Automatable
no
Technical impact
partial

Vulnrichment: CISA's decision-tree inputs.

Get told when this record changes

  • Not in KEV: no record of exploitation in the wild
  • No public exploit code on record
  • A fix has been released

If any of these changes, we'll tell you in the daily email digest.

Follow CVE-2021-47334

When you'll hear from us

  • when it enters CISA KEV
  • when exploit code appears or is weaponized
  • when the record is updated (including a fixed version)
  • when EPSS rises 20 points in a week

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Noroxi analysis

What does it mean in your environment?

The assessment above is generated automatically from the record's data; it doesn't know your environment. Our team verifies on your systems whether this vulnerability is actually exploitable and which mitigation is enough.

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Affected systems

Is your version affected?

Pick the product and type the version you run. It's compared with this record's version ranges in your browser; the version isn't sent anywhere.

VendorProduct
linuxlinux kernel

Affected versions

NVD version ranges (for catalog products). Add the product to your stack with a version and matching uses these.

  • linux linux kernelbefore 4.4.276
  • linux linux kernel4.5 and later · before 4.9.276
  • linux linux kernel4.10 and later · before 4.14.240
  • linux linux kernel4.15 and later · before 4.19.198
  • linux linux kernel4.20 and later · before 5.4.134
  • linux linux kernel5.5 and later · before 5.10.52
  • linux linux kernel5.11 and later · before 5.12.19
  • linux linux kernel5.13 and later · before 5.13.4

Versions reported by the vendor

Affected version ranges reported by the assigning authority (Linux). Independent of NVD's CPE analysis and usually ahead of it.

  • Linux Linux

    • 2.6.16affected
    • 736ce43295682d060f2b93624b4a339f9af6aab1 and later · before 1512e7dc5eb08b7d92a12e2bfcd9cb8c4a1ec069affected · git
    • 736ce43295682d060f2b93624b4a339f9af6aab1 and later · before 29ba8e2ba89ee2862a26d91204dd5fe77ceee25aaffected · git
    • 736ce43295682d060f2b93624b4a339f9af6aab1 and later · before 5b06ca113bf197aab2ab61288f42506e0049fbabaffected · git
    • 736ce43295682d060f2b93624b4a339f9af6aab1 and later · before 481a76d4749ee3a27f902ba213fdcbb4bb39720eaffected · git
    • 736ce43295682d060f2b93624b4a339f9af6aab1 and later · before 38660031e80eaa6cc9370b031c180612f414b00daffected · git
    • 736ce43295682d060f2b93624b4a339f9af6aab1 and later · before b9c87ce3bc6331f82811a8cf8e930423c22523a3affected · git
    • 736ce43295682d060f2b93624b4a339f9af6aab1 and later · before ef1067d2baa847d53c9988510d99fb494de4d12caffected · git
    • 736ce43295682d060f2b93624b4a339f9af6aab1 and later · before a7268e8a227d5a4f0bd1584f556246b0224ab274affected · git
    • 736ce43295682d060f2b93624b4a339f9af6aab1 and later · before 7272b591c4cb9327c43443f67b8fbae7657dd9aeaffected · git

Package-level exposure

OSV and GitHub Advisory data: ecosystem, package and range. SBOM matching uses this table.

EcosystemPackageAffected rangeFix
Debian:12linuxbefore 5.14.6-15.14.6-1

Same product

linux: all records

Other highest-scoring records for the same primary product.

  • CVE-2026-31431crypto: algif_aead - Revert to operating out-of-placeKEV
    90Now
  • CVE-2022-0847A flaw was found in the way the "flags" member of the new pipe buffer structure was lacking proper initialization in copy_page_to_iter_pipe KEV
    89Now
  • CVE-2021-22555Heap Out-Of-Bounds Write in Netfilter IP6T_SO_SET_REPLACEKEV
    85Now

Published before and after this one in the same product

  • ← EarlierCVE-2021-47332May 21, 2024 · ALSA: usx2y: Don't call free_pages_exact() with NULL address
    22Monitor
  • ← EarlierCVE-2021-47333May 21, 2024 · misc: alcor_pci: fix null-ptr-deref when there is no PCI bridge
    22Monitor
  • Later →CVE-2021-47335May 21, 2024 · f2fs: fix to avoid racing on fsync_entry_slab by multi filesystem instances
    22Monitor

Remediation

Which version to upgrade to

Fix versions compiled from the vendor, package registries and Microsoft. Verify the vendor's note before upgrading.

Product / packageFixed versionSource
Linux Linux1512e7dc5eb08b7d92a12e2bfcd9cb8c4a1ec069Vendor (CNA)
Linux Linux29ba8e2ba89ee2862a26d91204dd5fe77ceee25aVendor (CNA)
Linux Linux38660031e80eaa6cc9370b031c180612f414b00dVendor (CNA)
Linux Linux481a76d4749ee3a27f902ba213fdcbb4bb39720eVendor (CNA)
Linux Linux5b06ca113bf197aab2ab61288f42506e0049fbabVendor (CNA)
Linux Linux7272b591c4cb9327c43443f67b8fbae7657dd9aeVendor (CNA)
Linux Linuxa7268e8a227d5a4f0bd1584f556246b0224ab274Vendor (CNA)
Linux Linuxb9c87ce3bc6331f82811a8cf8e930423c22523a3Vendor (CNA)
Linux Linuxef1067d2baa847d53c9988510d99fb494de4d12cVendor (CNA)
debian:linux5.14.6-1 · Debian:12Package registry (OSV)

Exploit status

No known public exploit

No public exploit has been observed yet. That doesn't mean you're safe, only that the bar is a little higher.

Research context

For pentesters and researchers: attack profile, score disagreement, timeline, patch commits, credits, variant and chain candidates, bug bounty scope. All derived from existing data; no exploit code.

Timeline

From publication to today: proof of concept, Metasploit module, CISA KEV and fix record. Dates are as reported by the sources.

No dated events beyond publication.

No history yet (it accumulates with the daily EPSS job).

Patch and commit links

Commit, PR and diff links among the references. A starting point for patch-diffing and variant hunting; fixes, not exploits.

No commit or PR link among the references.

Credits

All researchers

Finders, reporters and analysts named in the CNA record. Click a name for that researcher’s other records.

No credits in the CNA record.

Variant candidates

Same product, same weakness class, within 18 months. If the patch missed the root cause, the sibling bug is here.

No nightly-computed relations.

Chain candidates

An authentication bypass and a privilege-requiring bug in the same product, published close together: combined they may become an unauthenticated path.

—

Bug bounty scope

No known public program.

Source: bounty-targets-data (public HackerOne, Bugcrowd, Intigriti, YesWeHack listings).

National notice (Türkiye Cybersecurity Directorate / USOM)

Official security notices citing this record; remediation advice is on the agency's page.

All national notices →

Technical details

Attack conditions

  • Someone with local access to the system can trigger it.
  • A low-privileged account is enough.
  • No user action is required.
  • No special conditions are required; it is repeatable.

If successful

Confidentiality
high · data can be read
Integrity
high · data or configuration can be modified
Availability
high · the service can be disrupted
Attack vector
Local
Attack complexity
Low
Privileges required
Low
User interaction
None
Scope
Unchanged
Confidentiality impact
High
Integrity impact
High
Availability impact
High

Weakness class (CWE)

CWE-416 · Use After Free

CVSS vector

CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H

nvd-primary

Root cause

After a memory region is freed, another reference pointing to it is still used. By then, the same region may have been allocated for different data.

The bug in code

The whole CWE-416 class

A representative example of this vulnerability class. Not the vendor's source code; it shows the faulty pattern and its fix.

Vulnerable

c
free(dev->buf);/* ... another thread is still running ... */process(dev->buf);

Fixed

c
lock(&dev->lock);free(dev->buf);dev->buf = NULL;unlock(&dev->lock);

Attack context

MITRE CAPEC attack patterns and ATT&CK techniques for this weakness class (CWE). A starting point for detection rules and threat hunting.

MITRE has no CAPEC/ATT&CK mapping for this CWE.

Change log

  1. Fix✗ → ✓

For records you follow, these changes also arrive as notifications. →

References

Show all references (8 more)

Vendor advisories and official records. Exploit/PoC links are deliberately left out.

All records