FedoraOperating system · Fedoraproject
CVE-2021-42380
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 clrvar 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 · high confidenceA use-after-free vulnerability exists in BusyBox's awk applet within the clrvar function. When processing a specially crafted awk pattern, the function incorrectly handles variable references, leading to memory corruption that can cause denial of service and potentially allow 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>= 1.28.0, <= 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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Check if BusyBox is installedRun 'busybox --version' or 'rpm -q busybox' to retrieve the installed BusyBox versionAffected if The version returned is between 1.28.0 and 1.33.1 inclusive
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Verify awk applet is availableRun 'busybox --list | grep awk' or check if the 'awk' symlink/command exists (ls -l $(which awk))Affected if The awk applet is present and executable in the BusyBox binary
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Confirm awk functionality is in useCheck if any scripts, services, or processes invoke awk, gawk, mawk, or the BusyBox awk applet directly (grep -r 'awk' /etc /opt /home 2>/dev/null | head -20)Affected if Any awk usage is found in the environment using the vulnerable BusyBox binary
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Identify the specific BusyBox binaryRun 'file $(which busybox)' and check package manager info 'rpm -qi busybox' (or equivalent dpkg/apt for non-Fedora systems)Affected if The binary is from a package matching the affected Fedora versions or falls within the 1.28.0-1.33.1 version range
You are affected if BusyBox is installed with a version between 1.28.0 and 1.33.1 and the awk applet is enabled and accessible in your environment.
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 vulnerability. If the awk applet is not required in the deployment, it can be disabled as a defense-in-depth measure.
Busybox 1.34.0 or later; Fedora 35 or later
- 1. Identify the current Busybox version using: busybox --version or rpm -q busybox
- 2. For Busybox installations: Upgrade to version 1.34.0 or later which contains the fix for the use-after-free in the awk applet
- 3. For Fedora systems: Fedora 33 and 34 are End-of-Life; migrate to a supported Fedora release (Fedora 35 or later) which includes the patched Busybox version
- 4. After upgrade, verify the fix by checking: busybox --version to confirm version 1.34.0+ is installed
- 5. Test awk functionality to ensure the clrvar function works correctly with: busybox awk 'BEGIN { print "test" }'
Generated from the published advisory — verify against the referenced sources before acting.
Fix this in Fedora
Scoped from the published advisory
- Consultation3.0 h
- Implementation6.0 h
- Testing4.0 h
- Review / QA2.0 h
An estimate, not a bill — we confirm scope with you before any work starts. Need it this week? Rush from $4,224.
Scan for this in your stack
Free · runs locallyCheck whether your project pulls in CVE-2021-42380 — 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-2021-42380 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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- Version or environment caveats, and links to real fixes
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