dbcve.org
FedoraOperating system · Fedoraproject

CVE-2021-42376

MEDIUM · 5.5 CVSS v3.1 Published 2021-11-15
Fix available
A fix is available. Upgrade to 1.34.0 or later.
See remediation →
57/100
Remediation priority · Elevated
Zero-click

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 · unedited
A NULL pointer dereference in Busybox's hush applet leads to denial of service when processing a crafted shell command, due to missing validation after a \x03 delimiter character. This may be used for DoS under very rare conditions of filtered command input.

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 confidence

A NULL pointer dereference vulnerability in Busybox's hush shell applet allows denial of service when processing specially crafted shell commands containing a \x03 delimiter character without proper validation after the delimiter.

MitigationUpdate Busybox to a patched version that includes proper validation after \x03 delimiter characters, or implement input filtering to reject commands containing \x03 characters if upstream updates are unavailable.

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
Affected:= 33= 34
BusyboxApplication
Affected:>= 1.16.0, < 1.34.0
Cloud BackupApplication
Affected:all versions
Hci Management NodeApplication
Affected:all versions
SolidfireApplication
Affected:all versions
H300s FirmwareOperating system
Affected:all versions
H500s FirmwareOperating system
Affected:all versions
H700s FirmwareOperating system
Affected:all versions

CVSS 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
Local
Complexity
Low
Privileges
Low
User interaction
None
Scope
Unchanged
Confidentiality
None
Integrity
None
Availability
High

CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/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 checks

Work through these to decide whether this CVE applies to you.

  1. Identify Busybox version
    Run 'busybox --version' or 'rpm -q busybox' to get the installed version number
    Affected if Version is >= 1.16.0 and < 1.34.0, or version cannot be determined on an affected Fedora release (33 or 34)
  2. Confirm hush shell is available
    Run 'busybox --list | grep hush' or attempt to invoke hush with 'busybox sh' to verify the hush applet is compiled and accessible
    Affected if The hush shell applet is present and can be invoked
  3. Verify hush is the default or configured shell
    Check if /bin/sh or /bin/bash links to busybox by running 'ls -la /bin/sh /bin/bash' and examining their target
    Affected if /bin/sh or the configured system shell resolves to busybox, meaning hush may be used for script execution
  4. Test for NULL pointer dereference trigger
    Execute a command containing the \x03 character in hush shell: echo 'test\x03' | busybox sh -c 'read line; echo $line'
    Affected if The command causes a crash, segmentation fault, or unexpected termination of the shell process

You are affected if Busybox version is between 1.16.0 and 1.34.0 (exclusive of 1.34.0), or if you run Fedora 33 or 34 with any Busybox version, and the hush shell applet is enabled and can be invoked.

Generated from the published advisory. Verify against your own configuration.

Check your environment

Paste your version and any relevant configuration and it will be compared against the affected criteria above. Do not include secrets or credentials.

AI-assisted, checked against the advisory. Informational, not a guarantee.

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 · scoped
Upgrade available Upgrade to 1.34.0 or later
Fixed in 1.34.0
Interim mitigation

Update Busybox to a patched version that includes proper validation after \x03 delimiter characters, or implement input filtering to reject commands containing \x03 characters if upstream updates are unavailable.

Recommended fix High confidence

Busybox 1.34.0 or later / Fedora 35 or later

  1. For Busybox-based systems: Upgrade Busybox to version 1.34.0 or later. This is the primary fix for the vulnerability.
  2. For Fedora systems: Upgrade Fedora to version 35 or later, which includes the fixed Busybox version.
  3. After upgrading, verify the Busybox version by running: busybox --version
  4. For appliance/firmware products (H300s/H500s/H700s, Cloud Backup, HCI Management Node, Solidfire): Contact the respective vendors (NetApp for Solidfire, Dell EMC for H-series) for firmware updates that address this Busybox vulnerability.
Caveat Minimal risk - this is a bugfix release. However, always test in a non-production environment first, as minor behavioral changes in shell builtins are possible.

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
  • Testing3.0 h
  • Review / QA1.0 h
7.0 hours of engineering $1,210
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References Go to the primary sourcePrimary sources — vendor advisories, patches and trackers. Where our summary and a reference disagree, the reference wins.

Primary sources

Practitioner notes

Contributed

Peer-ranked notes from engineers who’ve handled CVE-2021-42376 in production — separate from our analysis above.

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What this is

A place for practitioners to share what actually worked: a mitigation you’ve tested, a configuration change, a version- or environment-specific caveat, or a link to a verified patch. The most useful notes rise to the top as peers upvote them, so the signal stays high.

What belongs here
  • 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
  • No spam, self-promotion, credentials, or personal data