CVE-2021-20039
HighExploitedPublic exploitImproper 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.
Published Jan 4, 2022 · Updated Sep 5, 2025
Key Facts
Patch immediately- CVE-2021-20039 is a high-severity vulnerability (CVSS 8.8 v3.1) affecting Sma 200 Firmware (Sonicwall), Sma 210 Firmware (Sonicwall), Sma 400 Firmware (Sonicwall) and 3 more products.
- It is exploited in the wild, listed in Industry KEV feed since Mar 30, 2024. Public exploit code is available.
- EPSS estimates a 79% probability of exploitation in the next 30 days.
- No fixed version is listed yet; check the vendor advisory for mitigations.
- Brandefense priority: patch immediately, because it is listed as exploited in the wild.
CVSS v3.1
8.8
CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
EPSS (30-day exploit likelihood)
79%
Higher than 99.5% of all scored CVEs
Exploited in the wild
Yes
1 catalog listing
Public exploit code
Available
Proof-of-concept or weaponized module
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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.
Known-Exploited Catalog Listings
| Catalog | Added | Remediation due | Ransomware use |
|---|---|---|---|
| Industry KEV feed | Mar 30, 2024 | n/a | Not reported |
Required action: Apply remediations or mitigations per vendor instructions or discontinue use of the product if remediation or mitigations are unavailable.
Affected Products
16 affected entries in total| Product | Affected versions | Fixed in |
|---|---|---|
| Sma 200 FirmwareSonicwall | 10.2.0.8-37sv, 10.2.1.1-19sv, 9.0.0.11-31sv | n/a |
| Sma 210 FirmwareSonicwall | 10.2.0.8-37sv, 10.2.1.1-19sv, 9.0.0.11-31sv | n/a |
| Sma 400 FirmwareSonicwall | 10.2.0.8-37sv, 10.2.1.1-19sv, 9.0.0.11-31sv | n/a |
| Sma 410 FirmwareSonicwall | 10.2.0.8-37sv, 10.2.1.1-19sv, 9.0.0.11-31sv | n/a |
| Sma 500v FirmwareSonicwall | 10.2.0.8-37sv, 10.2.1.1-19sv, 9.0.0.11-31sv | n/a |
Timeline
Publicly disclosed
Jan 4, 2022
Added to Industry KEV feed
Mar 30, 2024
Last updated
Sep 5, 2025
Weakness Type
- CWE-78 Improper Neutralization of Special Elements used in an OS Command ('OS Command Injection')
References
- advisoryhttps://psirt.global.sonicwall.com/vuln-detail/SNWLID-2021-0026
- advisoryhttps://securityaffairs.co/
- advisoryhttps://securityaffairs.co/wordpress/125400/security/sonicwall-sma-100-devices-flaws.html
- advisoryhttps://threatpost.com/critical-sonicwall-vpn-bugs-appliance-takeover/176869/
- advisoryhttps://us-cert.cisa.gov/ncas/current-activity/2021/12/08/sonicwall-releases-security-advisory-sma-100-series-appliances
FAQ
Common Questions.
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.
Affected: Sma 200 Firmware (Sonicwall) versions 10.2.0.8-37sv, 10.2.1.1-19sv, 9.0.0.11-31sv; Sma 210 Firmware (Sonicwall) versions 10.2.0.8-37sv, 10.2.1.1-19sv, 9.0.0.11-31sv; Sma 400 Firmware (Sonicwall) versions 10.2.0.8-37sv, 10.2.1.1-19sv, 9.0.0.11-31sv, among others. The full list is in the CVE brief.
It is exploited in the wild, listed in Industry KEV feed since Mar 30, 2024.
No, it is not currently listed in the CISA Known Exploited Vulnerabilities catalog.
Public exploit code is available.
No fixed version is listed yet; check the vendor advisory for mitigations.
Brandefense priority: patch immediately, because it is listed as exploited in the wild.
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