FedoraOperating system · Fedoraproject
CVE-2021-42386
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 nvalloc 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 nvalloc function. An attacker can trigger this by providing a specially crafted awk pattern, causing memory corruption that leads 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>= 1.16.0, <= 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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Confirm BusyBox is installedRun 'busybox --version' or 'which busybox' to verify BusyBox is present on the systemAffected if BusyBox is installed and the version falls within 1.16.0 to 1.33.1
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Check the installed BusyBox versionExecute 'busybox --version' and compare the output against the affected range (>= 1.16.0 and <= 1.33.1)Affected if The version number is between 1.16.0 and 1.33.1 inclusive
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Verify the awk applet is availableRun 'busybox --help' or 'busybox awk --help' to confirm the awk applet is compiled and accessibleAffected if The awk applet is present and enabled in the BusyBox binary
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Check if awk is the default system awkRun 'which awk' to determine if busybox awk is being used as the system's default awk interpreterAffected if BusyBox awk is used as the primary awk implementation on the system
A system is affected if it runs BusyBox version 1.16.0 through 1.33.1 with the awk applet enabled and accessible, especially if busybox awk is the default awk implementation.
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 containing the fix for CVE-2021-42386. If immediate patching is not possible, consider restricting or disabling the awk applet until the update can be applied.
Busybox 1.34.0 or later (or equivalent patched vendor package for Fedora 33/34)
- Upgrade Busybox to version 1.34.0 or later to resolve the use-after-free vulnerability in the awk applet's nvalloc function
- For Fedora systems, apply the vendor security update: `dnf update busybox` or `dnf update --refresh` to install the patched busybox package
- Verify the upgrade was successful by checking the busybox version with: `busybox --version`
- Test that awk functionality works correctly after the update using: `echo 'test' | awk '{print $1}'`
Generated from the published advisory — verify against the referenced sources before acting.
Fix this in Fedora
Scoped from the published advisory
- Consultation2.0 h
- Implementation4.0 h
- Testing3.0 h
- Review / QA1.0 h
An estimate, not a bill — we confirm scope with you before any work starts. Need it this week? Rush from $2,800.
Scan for this in your stack
Free · runs locallyCheck whether your project pulls in CVE-2021-42386 — 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-2021-42386 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
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