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Fencer Vulns
critical 9.8

CVE-2021-20038 kev+ ransomware in the critical feed json

A Stack-based buffer overflow vulnerability in SMA100 Apache httpd server's mod_cgi module environment variables allows a remote unauthenti…

published 2021-12-08 4 y ago modified 2026-06-17 4 mo ago also EUVD-2021-7501

cvss
9.8
version 3.1, CNA
cisa kev
Exploited
added 2022-01-28, used in ransomware
epss
99.9%
EPSS 99.9% chance of exploitation in 30 days, percentile 99.9%
public exploits
1
Metasploit, plus a Nuclei check

Summary

A Stack-based buffer overflow vulnerability in SMA100 Apache httpd server's mod_cgi module environment variables allows a remote unauthenticated attacker to potentially execute code as a 'nobody' user in the appliance. This vulnerability affected SMA 200, 210, 400, 410 and 500v appliances firmware 10.2.0.8-37sv, 10.2.1.1-19sv, 10.2.1.2-24sv and earlier versions.

Patch / fix

cisa required action Apply updates per vendor instructions.

Timeline

  1. Published
  2. First public exploit (Metasploit exploit/linux/http/sonicwall_cve_2021_20039)
  3. Added to CISA KEV
  4. CISA patch deadline
  5. CISA SSVC: exploitation active

Known exploited

Added
4 y ago
Patch by
2022-02-11 (4 y ago)
Ransomware
Known to be used in ransomware campaigns
Required action
Apply updates per vendor instructions.
Vendor, product
SonicWall, SMA 100 Appliances
CISA name
SonicWall SMA 100 Appliances Stack-Based Buffer Overflow Vulnerability

CISA SSVC

Exploitation
Active, exploited in the wild
Automatable
yes
Technical impact
total
Assessed
21 mo ago

Exploit prediction

99.91% chance of exploitation in the next 30 days, higher than 99.9% of all scored CVEs (FIRST EPSS, 2026-11-08).

Exploits and checks

  • Metasploit exploit/linux/http/sonicwall_cve_2021_20039 SonicWall SMA 100 Series Authenticated Command Injection metasploit exploit, excellent rank, 2021-12-14
  • Nuclei template SonicWall SMA100 Stack - Buffer Overflow/Remote Code Execution nuclei detection template
  • github.com https://github.com/jbaines-r7/badblood referenced PoC, tagged "exploit" by a source, unverified
  • rapid7.com https://www.rapid7.com/blog/post/2022/01/11/cve-2021-20038-42-sonicwall-sma-100-multiple-vulnerabilities-fixed-2/ referenced PoC, tagged "exploit" by a source, unverified

CVSS scores

assigned by version score vector
CISA ADP 3.1 9.8 CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
NVD 3.1 9.8 CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
CNA 3.1 9.8 CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
NVD 2.0 7.5 AV:N/AC:L/Au:N/C:P/I:P/A:P

Affected products

  • SonicWall SonicWall SMA100

Classification

Weakness

References

Sources

Fencer Vulns keeps one entry per vulnerability: the CVE id wins, then GHSA, and records that alias each other are merged, except that two CVEs always keep separate entries. The same data is available as JSON.