FedoraOperating system · Fedoraproject
CVE-2021-42381
Official description Straight from the sourceThe vendor's or NVD's own wording, published unedited. Authoritative, but often terse — it says what broke, rarely what to do.
NVD · uneditedA 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 hash_init function
Technical summary Written by usOur analysis, written from the advisory, the CVSS vector and the affected-version data. It adds context the advisory leaves out, and never invents facts that are not in the source.
dbcve analysis · moderate confidenceA use-after-free vulnerability exists in BusyBox's awk applet within the hash_init function. When processing a specially crafted awk pattern, memory is freed but subsequently accessed, leading to denial of service and potentially arbitrary code execution.
Verify against the referenced sources before acting — the references below are authoritative for this CVE, this summary is not.
Affected products & versions What the vendor confirmedThe version ranges the vendor confirmed as vulnerable. If your version sits inside a range here, treat yourself as exposed until you have upgraded.
NVD · CPE data
FedoraOperating system
= 33= 34>= 1.21.0, <= 1.33.1CVSS breakdown How the score is builtThe industry scoring standard. It rates how the flaw is reached, what it takes to exploit, and what an attacker gains — the score is derived from those, not the other way round.
From the vector- Attack vector
- Network
- Complexity
- Low
- Privileges
- High
- User interaction
- None
- Scope
- Unchanged
- Confidentiality
- High
- Integrity
- High
- Availability
- High
CVSS:3.1/AV:N/AC:L/PR:H/UI:N/S:U/C:H/I:H/A:H
Am I affected? How to checkSteps we derive from the advisory and the affected-version data, so you can decide whether this CVE reaches your setup. They are a guide, not a scan — your own configuration is the authority.
dbcve checksWork through these to decide whether this CVE applies to you.
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Identify BusyBox installation and versionRun `busybox --version` or `busybox --help` to display the installed BusyBox version numberAffected if Version displays as between 1.21.0 and 1.33.1 inclusive (for example, 1.33.1 shows the vulnerability is present)
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Verify awk applet is availableRun `busybox awk --help` or `which awk` to confirm the awk applet is accessible in the environmentAffected if The awk command is available and resolves to BusyBox's awk applet (output shows BusyBox awk usage information)
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Confirm BusyBox was built with awk supportRun `busybox --list | grep awk` to list all available applets and verify awk is included in the buildAffected if The output includes 'awk' indicating the applet was compiled into the BusyBox binary being used
User is affected if BusyBox version is 1.21.0 through 1.33.1 and the awk applet is accessible and being used to process untrusted awk patterns.
Generated from the published advisory. Verify against your own configuration.
Remediation Closing itWhat it takes to close this. Where a vendor fix exists we point at it; where none exists we say so plainly, and can build one. Effort estimates are scoped from the advisory, not from your codebase.
dbcve · scopedUpdate BusyBox to a version that includes the fix for this use-after-free vulnerability in the awk applet's hash_init function.
Busybox 1.33.2 or later (or latest stable release)
- Check the currently installed Busybox version using: rpm -q busybox or dpkg -l busybox
- Update Busybox to version 1.33.2 or later using the system package manager: dnf update busybox (Fedora) or apt-get update && apt-get install busybox (Debian-based)
- Verify the updated version: busybox --version
- Ensure the awk applet is updated: which awk and verify it points to the updated Busybox
Generated from the published advisory — verify against the referenced sources before acting.
Fix this in Fedora
Scoped from the published advisory
- Consultation2.0 h
- Implementation1.0 h
- Testing8.0 h
- Review / QA3.0 h
An estimate, not a bill — we confirm scope with you before any work starts. Need it this week? Rush from $3,712.
Scan for this in your stack
Free · runs locallyCheck whether your project pulls in CVE-2021-42381 — or any other known-vulnerable package — straight from your lock files. Free and open source; it runs locally and uploads nothing.
References Go to the primary sourcePrimary sources — vendor advisories, patches and trackers. Where our summary and a reference disagree, the reference wins.
Primary sourcesPractitioner notes
ContributedPeer-ranked notes from engineers who’ve handled CVE-2021-42381 in production — separate from our analysis above.
The advisory tells you what broke. It rarely tells you what actually worked. If you’ve dealt with this one, that detail is what the next engineer is searching for.
- The version that genuinely resolved it — not the one the vendor claimed
- A config change or rule that shut the vector down
- A gotcha in the upgrade path that cost you an afternoon
No notes yet
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- Verified mitigations, workarounds, and config changes
- Version or environment caveats, and links to real fixes
- No weaponised exploit code, or anything meant to cause harm
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