Vulnerability · CVE-2021-4473
topsecgroup tianxin_internet_behavior_management_system Improper Neutralization of Special Elements used in an OS Command ('OS Command Injection')
Published Apr 6, 2026 · corrected/updated Jun 17, 2026 · Beijing Topsec Network Security Technology Co., Ltd. Tianxin Internet Behavior Management System · evidence confidence very high
Tianxin 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).
Grounded briefings
Catalog interpretations for three audiences. Each brief cites ingested metadata and the original advisories below. They are not independent research and they do not invent exploit steps.
Executive
CVE-2021-4473 is a critical public vulnerability record for Beijing Topsec Network Security Technology Co., Ltd. Tianxin Internet Behavior Management System. CISA lists it as known exploited. Published remediation guidance: Apply remediations or mitigations per vendor instructions or discontinue use of the product if remediation or mitigations are unavailable. This summary is a catalog interpretation of the ingested metadata and cites the original advisories below.
System administrator
Identify whether Beijing Topsec Network Security Technology Co., Ltd. Tianxin Internet Behavior Management System is in your estate, then compare installed versions with the affected ranges. Affected packages or ranges on record: topsecgroup/tianxin internet behavior management system; Beijing Topsec Network Security Technology Co., Ltd. Tianxin Internet Behavior Management System. Published remediation guidance: Apply remediations or mitigations per vendor instructions or discontinue use of the product if remediation or mitigations are unavailable. Prefer the vendor or distribution advisory linked in Sources before changing production systems. This is a catalog interpretation, not a runbook.
Security analyst
Signals on file: CVSS 9.3 (technical impact); EPSS 6.2% (30-day exploitation probability). CISA lists it as known exploited. Weakness classes: CWE-78. Sources contributing to this record: cve_org, epss, nvd, vulncheck_kev. Public exploit references, when present, are outbound links only and are not proof of active exploitation. This is a catalog interpretation of stored metadata.
Exploitation and remediation
Exploitation evidence
Confirmed in CISA KEV since Apr 6, 2026. Listed in CISA KEV and VulnCheck KEV.
Patch and remediation
Apply remediations or mitigations per vendor instructions or discontinue use of the product if remediation or mitigations are unavailable.
Safe detection guidance
Compare installed versions with the affected ranges below and verify the advisory from the original publisher. This site stores metadata and outbound links only; it does not ship exploit code or proof-of-concept payloads.
Code
The project this record applies to. Exploit listings stay in References.
No public source repository is identified for this product.
Timeline
Detection, updates, and resolution for this record.
Apr 6, 2026 · CISA KEV
Known exploited
Apply remediations or mitigations per vendor instructions or discontinue use of the product if remediation or mitigations are unavailable.
Apr 7, 2026 · NIST NVD
Detected
Tianxin 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
Jun 17, 2026 · NIST NVD
Updated
Tianxin 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
Affected
Enter an installed version to get a verified affected / not-affected result against the ranges below.
- cpe topsecgroup/tianxin internet behavior management systemversion unspecified
- vendor Beijing Topsec Network Security Technology Co., Ltd. Tianxin Internet Behavior Management Systemversion unspecified
Sources
- CVE.orgVulnerability recordCVE-2021-4473
Official CVE identifier
cve.org - FIRST EPSSExploitation probabilityCVE-2021-4473
30-day exploitation probability 6.2%
first.org - NIST NVDVulnerability recordCVE-2021-4473
Tianxin 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 redir
nvd.nist.gov - VulnCheck KEVConfirmed exploitationCVE-2021-4473
Tianxin 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 redir
vulncheck.com