CVE-2021-42381Network attack vector

Denial of service via awk hash use-after-free

Published Nov 15, 2021 · Updated Nov 3, 2025

Use-after-free in BusyBox awk before 1.34.0 allows remote authenticated users to cause denial of service or code execution via crafted patterns. The awk hash_init function frees hash data and then reuses it while processing attacker-controlled pattern text, creating a dangling-pointer access. Exploitation requires access to invoke awk with a crafted pattern; consequences range from process interruption to possible code execution.

CVSS severity7.2
High
EPSS probability2.77%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Use-after-free in BusyBox awk before 1.34.0 allows remote authenticated users to cause denial of service or code execution via crafted patterns. The awk hash_init function frees hash data and then reuses it while processing attacker-controlled pattern text, creating a dangling-pointer access. Exploitation requires access to invoke awk with a crafted pattern; consequences range from process interruption to possible code execution.

The record

CVE
CVE-2021-42381
Published
Nov 15, 2021
Updated
Nov 3, 2025
Vendor
BusyBox
Product
BusyBox
Classifications
CWE-416, T1203
Attack vector
network
Privileges
authenticated

Timeline

How it unfolded

  1. Nov 15, 2021CVE publishedPublication date reported by the CVE source.
  2. Nov 3, 2025Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

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Is a vulnerable build present?

Compare these published version ranges with your installed build and any vendor patches.

  1. Affected versionversion=unspecified <1.34.0

What conditions does exploitation require?

Attack vectornetwork
Required privilegesauthenticated

What is affected?

BusyBox · BusyBoxversion=unspecified <1.34.0

Published CVSS scores

6.5TenableAV:N/AC:L/Au:S/C:P/I:P/A:P
7.2NVDCVSS:3.1/AV:N/AC:L/PR:H/UI:N/S:U/C:H/I:H/A:H

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

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No observations available

Sep 10, 2026Sep 16, 2026
Latest reporting daySep 16, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-416Use After Free
T1203Exploitation for Client Execution

Public exploit references

No public exploit references are available in this record.

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Technologies

Your stack

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Your stack

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