Unauthenticated code execution via unbounded CGI concatenation
Published Dec 8, 2021 · Updated Oct 21, 2025
Stack overflow in SonicWall SMA 100 Series 10.2.0.8-37sv and 10.2.1.2-24sv and earlier allows remote attackers to execute code. The modified mod_cgi cgi_build_command function uses strcat without bounds checks to append CGI environment variables, including QUERY_STRING, into one 202-byte stack buffer. No authentication or user interaction is required; successful exploitation runs code as nobody, while malformed requests can crash the automatically restarted HTTP service.
Summary
What happened
Stack overflow in SonicWall SMA 100 Series 10.2.0.8-37sv and 10.2.1.2-24sv and earlier allows remote attackers to execute code. The modified mod_cgi cgi_build_command function uses strcat without bounds checks to append CGI environment variables, including QUERY_STRING, into one 202-byte stack buffer. No authentication or user interaction is required; successful exploitation runs code as nobody, while malformed requests can crash the automatically restarted HTTP service.
The record
- CVE
- CVE-2021-20038
- Published
- Dec 8, 2021
- Updated
- Oct 21, 2025
- Vendor
- SonicWall
- Product
- Secure Mobile Access (SMA) 100 Series
- Classifications
- CWE-121, T1190
- Attack vector
- network
- Privileges
- unauthenticated
Timeline
How it unfolded
- Dec 8, 2021CVE publishedPublication date reported by the CVE source.
- Jan 28, 2022Exploitation reportedCISA Known Exploited Vulnerabilities Catalog entry
- Oct 21, 2025Record updatedLatest update available in the CVE record.
Exploitability
Present is not the same as exploitable
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Is a vulnerable build present?
Compare these published version ranges with your installed build and any vendor patches.
- Affected versionversion=10.2.0.8-37sv and earlier
- Affected versionversion=10.2.1.1-19sv and earlier
- Affected versionversion=10.2.1.2-24sv and earlier
What conditions does exploitation require?
What is affected?
Published CVSS scores
CVSS describes severity. EPSS estimates exploitation probability.
Attacks
What attackers are doing with it
Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.
Weakness, pattern, technique
Public exploit references
- Bad Bloodweaponized · demonstrated
Labels summarize the accepted research assessment. They do not indicate a test against your environment.
Reported exploitation
- CISA Known Exploited Vulnerabilities Catalog entryknown exploited catalog
Technologies
Your stack
See the directory against your own environment.
Your stack
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