Security readout for executives and security teams
Plain-English summary
CVE-2021-20038 is a critical remote code execution risk in SonicWall SMA100 appliances. An unauthenticated attacker could trigger a stack-based buffer overflow in Apache httpd mod_cgi environment variable handling and potentially run code as the appliance's 'nobody' user.
Executive priority
Treat this as urgent for any exposed SonicWall SMA100 appliance. It is critical severity, remotely reachable without authentication, and listed by CISA as known exploited. Confirm exposure and remediate vendor-identified affected firmware promptly.
Technical view
The vulnerability is CWE-121 in SMA100 Apache httpd mod_cgi environment variable processing. It affects SMA 200, 210, 400, 410, and 500v firmware 10.2.0.8-37sv, 10.2.1.1-19sv, 10.2.1.2-24sv, and earlier. CVSS is 9.8: network, low complexity, no privileges, no user interaction.
Likely exposure
Exposure is most likely where affected SMA100 VPN appliances are reachable from untrusted networks. Prioritize internet-facing SMA 200, 210, 400, 410, and 500v systems running the listed firmware branches or earlier.
Exploitation context
CISA lists CVE-2021-20038 in the Known Exploited Vulnerabilities catalog, so active exploitation is supported by a cited government source. The public source bundle also includes Rapid7 research and a GitHub reference, but this assessment does not rely on exploit details.
Researcher notes
Evidence supports unauthenticated remote code execution potential as the 'nobody' user through mod_cgi environment variable handling. The bundle identifies affected models and firmware, CVSS 9.8, CWE-121, and KEV status. It does not provide complete fixed-version details in the embedded text.
Mitigation direction
- Inventory all SonicWall SMA100 appliances and record exact firmware versions.
- Apply SonicWall PSIRT guidance and upgrade affected firmware to a vendor-fixed release.
- Prioritize internet-exposed SMA100 appliances before internal-only systems.
- Review vendor guidance for any temporary mitigations if immediate upgrade is not possible.
- Monitor appliance logs for suspicious web requests and unexpected process behavior.
Validation and detection
- Confirm whether each appliance is SMA 200, 210, 400, 410, or 500v.
- Compare firmware against 10.2.0.8-37sv, 10.2.1.1-19sv, and 10.2.1.2-24sv thresholds.
- Verify remediation status against SonicWall PSIRT SNWLID-2021-0026.
- Check CISA KEV tracking and internal asset exposure for prioritization.
- Review recent logs for anomalies before and after remediation.
Public sources used
Generated from the cited source records. This long-tail analysis has not been individually reviewed by a named human.
Conservative CVE-to-ATT&CK context
These mappings and lookup hints may be relevant to the vulnerability behavior, CWE, affected product, or exposure path. Glexia-inferred context is not an official MITRE, ATT&CK, CWE, or CVE Program mapping.
ATT&CK lookup starting points
Use these exact CWE pages and searches to review the Glexia ATT&CK library from this CVE's weakness and description context.
CWE-121: Exact CWE lookup
Use the exact CWE identifier as the starting point before reviewing related ATT&CK behavior. Open the exact CWE lookup page first, then review the ATT&CK searches from that MITRE weakness context. This is a Glexia lookup hint, not an official ATT&CK mapping.
Open ATT&CK lookupCVE-2021-20038 mapping review
Open the CVE-to-ATT&CK bridge for reviewed, inferred, or future official mappings tied to this CVE.
Open ATT&CK lookup- Severity
- Critical
- CVSS
- 9.8 (3.1)
- Known Exploited
- Yes
- Published
Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
CNA and ADP enrichment extracted from CVE v5
These fields come from the CVE record and ADP containers, not from Glexia's Take. They preserve time-varying source decisions such as CISA SSVC, KEV status, CVSS metrics, and provider references.
CISA KEV status
CVSS vector scores
1 official scoreWe collect every scored CVSS vector available in the official CNA and ADP containers. When more than one version is present, the table keeps the source vectors side by side instead of collapsing them into the highest score.
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H3.95.9Primary CVE scoreVulnerability scoring details
Base CVSS 3.1 score
9.8CriticalVector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
Source materials
- CVE List V5 sourceCVE List V5
- https://psirt.global.sonicwall.com/vuln-detail/SNWLID-2021-0026CVE reference · x_refsource_CONFIRM
- https://github.com/jbaines-r7/badbloodCVE reference · x_refsource_MISC
- https://www.rapid7.com/blog/post/2022/01/11/cve-2021-20038-42-sonicwall-sma-100-multiple-vulnerabilities-fixed-2/CVE reference · x_refsource_MISC
- https://www.cisa.gov/known-exploited-vulnerabilities-catalog?field_cve=CVE-2021-20038CVE reference · government-resource
Products and packages named in the record
CWE details
CWE links open Glexia weakness intelligence pages with official CWE context, developer remediation guidance, and related CVE mappings.
Stack-based Buffer Overflow
Stack-based Buffer Overflow represents a recurring weakness pattern that can create exploitable paths when design, validation, or implementation controls are missing.