CVE-2021-4473
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 · uneditedTianxin Internet Behavior Management System contains a command injection vulnerability in the Reporter component endpoint that allows unauthenticated attackers to execute arbitrary commands by supplying a crafted objClass parameter containing shell metacharacters and output redirection. Attackers can exploit this vulnerability to write malicious PHP files into the web root and achieve remote code execution with the privileges of the web server process. This vulnerability has been fixed in version NACFirmware_4.0.0.7_20210716.180815_topsec_0_basic.bin. Exploitation evidence was first observed by the Shadowserver Foundation on 2024-06-01 (UTC).
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 confidenceTianxin Internet Behavior Management System has a command injection vulnerability in its Reporter component endpoint. Unauthenticated attackers can inject shell metacharacters and output redirection through the objClass parameter to execute arbitrary OS commands, allowing them to write malicious PHP files to the web root and achieve remote code execution as the web server user.
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< 4.0.0.7_20210716.180815CVSS 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
- None
- User interaction
- None
- Scope
- Unchanged
- Confidentiality
- High
- Integrity
- High
- Availability
- High
CVSS:3.1/AV:N/AC:L/PR:N/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 if Tianxin Internet Behavior Management System is deployedLocate the Tianxin Internet Behavior Management System installation by identifying the web interface, typically accessible on ports 80/443. Check for Topsecgroup or Tianxin branding in the web application.Affected if The system is running Topsecgroup Tianxin Internet Behavior Management System.
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Determine the installed firmware versionAccess the system administration interface and navigate to the version information page, or check the firmware file currently installed on the device. Compare the version number to 4.0.0.7_20210716.180815.Affected if The installed version is less than 4.0.0.7_20210716.180815.
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Verify the Reporter component is accessibleAttempt to access the Reporter component endpoint. This is typically found at a path containing 'Reporter' or 'reporter' in the URL structure. Check if unauthenticated access is permitted.Affected if The Reporter component endpoint is exposed and reachable without authentication.
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Inspect web root for unexpected PHP filesExamine the web root directory (typically /var/www/html or similar) for any PHP files that were not authored by your organization. Look for files with suspicious names, recently created timestamps, or containing base64 encoded content or shell_exec calls.Affected if Unexpected PHP files exist in the web root, especially those containing shell execution commands.
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Review access logs for the vulnerable parameterSearch HTTP access logs for requests to the Reporter endpoint that contain the 'objClass' parameter. Look for shell metacharacters such as ; | & > < $ ( ) in the parameter values.Affected if Logs show requests to the Reporter endpoint with shell metacharacters in the objClass parameter.
The environment is affected if it runs Topsecgroup Tianxin Internet Behavior Management System version below 4.0.0.7_20210716.180815 with the Reporter component endpoint exposed to network traffic.
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 · scoped4.0.0.7_20210716.180815
Apply the vendor-supplied patch (NACFirmware_4.0.0.7_20210716.180815_topsec_0_basic.bin) to upgrade to the fixed firmware version. If immediate patching is not feasible, disable or restrict access to the Reporter component endpoint and deploy WAF rules to block shell metacharacters in HTTP parameters.
NACFirmware_4.0.0.7_20210716.180815_topsec_0_basic.bin (version 4.0.0.7_20210716.180815)
- Obtain the fixed firmware image: NACFirmware_4.0.0.7_20210716.180815_topsec_0_basic.bin from the vendor's official distribution channel
- Create a complete backup of the current system configuration and any custom settings
- Verify the integrity of the firmware image using checksums provided by the vendor
- If possible, deploy the firmware to a staging/test environment to validate compatibility with existing network configurations
- Schedule a maintenance window to apply the firmware upgrade
- Access the Tianxin Internet Behavior Management System administrative interface
- Navigate to the firmware update or system upgrade section
- Upload and apply the NACFirmware_4.0.0.7_20210716.180815_topsec_0_basic.bin firmware image
Generated from the published advisory — verify against the referenced sources before acting.
- Consultation3.0 h
- Implementation6.0 h
- Testing3.0 h
- Review / QA2.0 h
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Scan for this in your stack
Free · runs locallyCheck whether your project pulls in CVE-2021-4473 — 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-2021-4473 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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