Code execution or crash via evaluate use-after-free
Published Nov 15, 2021 · Updated Nov 3, 2025
Use-after-free in BusyBox awk before 1.34.0 allows attackers to crash the applet or possibly execute code via a crafted pattern. The evaluate function accesses an awk value after its storage has been freed while processing the attacker-controlled command-line pattern. The awk applet is not a daemon, so exposure requires another workflow to pass untrusted pattern input; a successful trigger crashes that process or executes code in its context.
Summary
What happened
Use-after-free in BusyBox awk before 1.34.0 allows attackers to crash the applet or possibly execute code via a crafted pattern. The evaluate function accesses an awk value after its storage has been freed while processing the attacker-controlled command-line pattern. The awk applet is not a daemon, so exposure requires another workflow to pass untrusted pattern input; a successful trigger crashes that process or executes code in its context.
The record
- CVE
- CVE-2021-42385
- Published
- Nov 15, 2021
- Updated
- Nov 3, 2025
- Vendor
- BusyBox
- Product
- BusyBox
- Classifications
- CWE-416
- Attack vector
- network
- Privileges
- admin
Timeline
How it unfolded
- Nov 15, 2021CVE publishedPublication date reported by the CVE source.
- 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?
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- Affected versionversion=unspecified <1.34.0
What conditions does exploitation require?
What is affected?
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.
Weakness, pattern, technique
Public exploit references
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Technologies
Your stack
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Your stack
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