HOMEVULNERABILITIESCVE-2021-20039
UNKNOWNCISA KEVIN THE WILD

CVE-2021-20039

Published: April 11, 2026

EPSS:82.46%probability of exploitation in 30 daysPercentile:99.2th

Official Description

Improper neutralization of special elements in the SMA100 management interface '/cgi-bin/viewcert' POST http method allows a remote authenticated attacker to inject arbitrary commands as a 'nobody' user. This vulnerability affected SMA 200, 210, 400, 410 and 500v appliances.

NVD Source

Technical Analysis

CVE-2021-20039 requires local access, meaning attackers must already have a foothold on the target system.

Exploitation requires some privileges, which limits the exposure to scenarios where an attacker has already gained initial access.

CISA has added CVE-2021-20039 to the Known Exploited Vulnerabilities (KEV) catalog, confirming active exploitation in the wild. U.S. federal agencies are required to patch this within the mandated timeframe, and all organizations should treat remediation as urgent.

Exploit & PoC Resources

ACTIVE EXPLOITATIONConfirmed exploitation in the wild
Exploit-DB
Offensive Security exploit database
GitHub PoC Search
Community PoC repositories
Rapid7 / Metasploit
Metasploit module search
PacketStorm
Security advisories & exploits
NVD Detail
Official NIST entry
MITRE CVE
CVE Program entry
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Quick Facts

CVE IDCVE-2021-20039
Severity—
CISA KEVYES — Active Exploitation
ExploitIN THE WILD
EPSS (30d)82.46%
PublishedApr 11, 2026

Recommended Actions

  • →Apply vendor patches immediately
  • →Monitor CVE-2021-20039 in threat intel feeds
  • →Review IDS/IPS signatures for exploitation attempts
  • !CISA KEV: Federal agencies must patch per BOD 22-01 timeline
  • !Active exploitation confirmed — treat as P1
Data sourced from NVD (NIST), CISA KEV, and EPSS (FIRST). Analysis generated by CTIWATCH.COM. CVE data is provided under the NVD usage policy.
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