NVD / CVE Program· CNA JFROG

CVE-2021-42380: A use-after-free in Busybox's awk applet leads to denial of service and possibly code execution when processing a crafted awk pattern in the

Noroxi assessment

Priority: Monitor (action score 29/100)

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: 3% (FIRST EPSS); higher than 87.7% of all records.
Anyone who can reach it over the internet can trigger it. Administrator privileges are required. No user action is required. No special conditions are required; it is repeatable.
Fixed version: busybox (Alpine:v3.11) 1.31.1-r11; busybox (Alpine:v3.12) 1.31.1-r21; busybox (Alpine:v3.13) 1.32.1-r7.

Low priority for now. Upgrade to busybox (Alpine:v3.11) 1.31.1-r11; busybox (Alpine:v3.12) 1.31.1-r21; busybox (Alpine:v3.13) 1.32.1-r7 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

A use-after-free in Busybox's awk applet leads to denial of service and possibly code execution when processing a crafted awk pattern in the clrvar function

HighCVSS 7.2 · v3.1—No exploit Fix available

Memory safety

Published: Nov 15, 2021
Updated: Jun 17, 2026
EPSS: 3.0% · 87th percentile
CWE: CWE-416

Report tools

JSON

Action score

Monitor

Low priority for now.

CVSS: 28 / 40 · 7.2 / 10
CISA KEV: 0 / 30 · Not listed
EPSS: 1 / 30 · 3.0%

CISA SSVC decision

Exploitation: none
Automatable: no
Technical impact: total

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

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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.

Vendor	Product	CPE
busybox	busybox	cpe:2.3:a:busybox:busybox
fedoraproject	fedora	cpe:2.3:o:fedoraproject:fedora

Affected versions

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

busybox busybox1.28.0 and later · up to 1.33.1 inclusive
fedoraproject fedora33
fedoraproject fedora34

Versions reported by the vendor

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

busybox busybox
- unspecified and later · before 1.34.0affected

Package-level exposure

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

Ecosystem	Package	Affected range	Fix
Alpine:v3.11	busybox	from 1.28.0 · before 1.31.1-r11	1.31.1-r11
Alpine:v3.12	busybox	from 1.28.0 · before 1.31.1-r21	1.31.1-r21
Alpine:v3.13	busybox	from 1.28.0 · before 1.32.1-r7	1.32.1-r7
Alpine:v3.14	busybox	from 1.28.0 · before 1.33.1-r6	1.33.1-r6
Alpine:v3.15	busybox	from 1.28.0 · before 1.34.0-r0	1.34.0-r0
Debian:11	busybox	before 1:1.30.1-6+deb11u1	1:1.30.1-6+deb11u1
Debian:12	busybox	before 1:1.35.0-1	1:1.35.0-1
SUSE:Linux Enterprise High Performance Computing 15 SP4-ESPOS	busybox	before 1.35.0-150400.3.14.1	1.35.0-150400.3.14.1
SUSE:Linux Enterprise Server 12 SP5-LTSS	busybox	before 1.35.0-10.3.1	1.35.0-10.3.1

Same product

busybox: all records

Other highest-scoring records for the same primary product.

CVE-2018-1000517BusyBox project BusyBox wget version prior to commit 8e2174e9bd836e53c8b9c6e00d1bc6e2a718686e contains a Buffer Overflow vulnerability in Bu
49Plan
CVE-2016-2148Heap-based buffer overflow in the DHCP client (udhcpc) in BusyBox before 1.25.0 allows remote attackers to have unspecified impact via vecto
47Plan
CVE-2022-48174There is a stack overflow vulnerability in ash.c:6030 in busybox before 1.35.
40Plan

Published before and after this one in the same product

← EarlierCVE-2021-42378Nov 15, 2021 · A use-after-free in Busybox's awk applet leads to denial of service and possibly code execution when processing a crafted awk pattern in the
29Monitor
← EarlierCVE-2021-42379Nov 15, 2021 · A use-after-free in Busybox's awk applet leads to denial of service and possibly code execution when processing a crafted awk pattern in the
29Monitor
Later →CVE-2021-42381Nov 15, 2021 · A use-after-free in Busybox's awk applet leads to denial of service and possibly code execution when processing a crafted awk pattern in the
29Monitor

Remediation

Which version to upgrade to

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

Product / package	Fixed version	Source
alpine:busybox	1.31.1-r11 · Alpine:v3.11	Package registry (OSV)
debian:busybox	1:1.35.0-1 · Debian:12	Package registry (OSV)
suse:busybox	1.35.0-150400.3.14.1 · SUSE:Linux Enterprise High Performance Computing 15 SP4-ESPOS	Package 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).

Technical details

Attack conditions

Anyone who can reach it over the internet can trigger it.
Administrator privileges are required.
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: Network
Attack complexity: Low
Privileges required: High
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:N/AC:L/PR:H/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

1free(dev->buf);
2/* ... another thread is still running ... */
3process(dev->buf);

Fixed

1lock(&dev->lock);
2free(dev->buf);
3dev->buf = NULL;
4unlock(&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

Fix✗ → ✓Sep 28, 2026, 10:48 PM UTC

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

References

claroty.com/team82/research/unboxing-busybox-14-vulnerabilities-uncovered-by-claroty-jfrog

Show all references (5 more)

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

All records