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CVE-2021-42379

25
FAUCET Score

CVE-2021-42379 describes a use-after-free vulnerability in the Busybox awk applet, affecting Busybox and Fedora distributions. This flaw can be triggered by processing a specially crafted awk pattern in the next_input_file function, leading to a denial of service and potentially arbitrary code execution. With a CVSS score of 7.2 (HIGH), it is a network-exploitable vulnerability requiring high privileges, but with low attack complexity, posing a significant risk of high impact to confidentiality, integrity, and availability. Currently, there is no evidence of active exploitation, public exploit code (Metasploit, Nuclei, ExploitDB), or significant community discussion or media coverage.

Impacted Technologies

VendorProductVersion(s)CPE
>= 1.18.0, <= 1.33.1CPE matchmatch criteria
cpe:2.3:a:busybox:busybox:*:*:*:*:*:*:*:*
33CPE matchmatch criteria
cpe:2.3:o:fedoraproject:fedora:33:*:*:*:*:*:*:*
34CPE matchmatch criteria
cpe:2.3:o:fedoraproject:fedora:34:*:*:*:*:*:*:*
< 1.34.0CPE match
cpe:2.3:a:busybox:busybox:*:*:*:*:*:*:*:*

CVSS Data

CVSS version used by this source: 3.1

7.2HIGH

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

Attack Vector
NETWORK
Attack Complexity
LOW
Privileges Required
HIGH
User Interaction
NONE
Scope
UNCHANGED
Confidentiality Impact
HIGH
Integrity Impact
HIGH
Availability Impact
HIGH
Exploitability Score
1.2
Impact Score
5.9
CvssVersion
3.1

Exploit Intelligence

EPSS Score
2.58%
Probability of exploitation in next 30 days
EPSS Percentile
83.6%
Percentile rank of EPSS score among Peer Group
As of 2026-07-28
Model: v2026.06.15
This CVE's current EPSS score of 0.0258 is in the 81st percentile among its peer group of 5,538 CVEs.

Social Chatter

The average CVE in this peer group has 0.0 Twitter, 0.0 Reddit, 0.1 Bluesky, 0.1 Mastodon, and 0.3 GitHub mentions.

Media Mentions

No media coverage found for this CVE.

The average CVE in this peer group has 0.1 InfoSec Media, 0.0 Vendor Blog, and 0.0 Security Researcher mentions.

Remediation

Patch Available

Vendor Patches (4)

microsoftpatch availablevia msrc
Product: 18965-16820Fixed in: 1.34.1-1
microsoftpatch availablevia msrc
Product: 18966-16823Fixed in: 1.35.0-1
microsoftpatch availablevia msrc
Product: cm1 busybox 1.34.1-1 on CBL Mariner 1.0Fixed in: 1.34.1-1
microsoftpatch availablevia msrc
Product: cbl2 busybox 1.35.0-1 on CBL Mariner 2.0Fixed in: 1.35.0-1

Vendor Advisories (2)

microsoft2021-Nov/CVE-2021-42379Important

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 next_input_file function

Nov 9, 2021
redhatCVE-2021-42379Moderate

busybox: use-after-free in awk applet leads to denial of service and possibly code execution when processing a crafted awk pattern in the next_input_file()

Nov 9, 2021

References

lists.debian.org / debian-lts-announce/2025/01/msg00012.html
claroty.com / team82/research/unboxing-busybox-14-vulnerabilities-uncovered-by-claroty-jfrog
jfrog.com / blog/unboxing-busybox-14-new-vulnerabilities-uncovered-by-claroty-and-jfrog
Third Party Advisory
lists.fedoraproject.org / archives/list/package-announce%40lists.fedoraproject.org/message/6T2TURBYYJGBMQTTN2DSOAIQGP7WCPGV
lists.fedoraproject.org / archives/list/package-announce%40lists.fedoraproject.org/message/UQXGOGWBIYWOIVXJVRKHZR34UMEHQBXS
security.netapp.com / advisory/ntap-20211223-0002
Third Party Advisory