# CVE-2021-20028 — SonicWall SRA/SMA100

**CISA KEV** · **Ransomware**

> As of 2025-10-21, CVE-2021-20028 is a CRITICAL-severity vulnerability in SonicWall SRA/SMA100, CVSS v3.1 9.8, EPSS 30.0% (98.1th percentile). It is listed in the CISA Known Exploited Vulnerabilities catalog (added 2022-03-28), with a US federal remediation deadline of 2022-04-18, and CISA links it to known ransomware campaigns. Threadlinqs Intelligence links 1 tracked threat campaign to CVE-2021-20028, most recently “Coordinated Reconnaissance Campaign Maps SonicWall SSL VPN Attack Surface via Commercial Proxy Infrastructure (84,142 Sessions / 4,305 IPs / 20 ASNs)”.

**Last updated:** 2025-10-21

## What is CVE-2021-20028?

Improper neutralization of a SQL Command leading to SQL Injection vulnerability impacting end-of-life Secure Remote Access (SRA) products, specifically the SRA appliances running all 8.x firmware and 9.0.0.9-26sv or earlier

The record classifies CVE-2021-20028 under weakness class [CWE-89](https://intel.threadlinqs.com/cwe/CWE-89). Its CVSS v3 base vector states that the flaw is reachable remotely over the network, needs no prior authentication, needs no user interaction, and has high impact on confidentiality, integrity, availability. 1 affected-product entry is recorded, across 1 vendor, listed below. The identifier was first published 1900 days ago.

## Severity and exploitation probability

- **CVSS v3.1 base score:** 9.8 — CRITICAL (`CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H`)
- **EPSS (FIRST):** 30.0% probability of exploitation in the next 30 days, higher than 98.1% of all scored CVEs
- **CISA KEV:** Listed since 2022-03-28, federal remediation deadline 2022-04-18 — used in known ransomware campaigns
- **Threadlinqs priority:** 10/10 — CISA lists it as used in ransomware, which Threadlinqs scores at the maximum
- **Published:** 2021-08-04, last modified 2025-10-21

## Is CVE-2021-20028 being exploited?

CISA added CVE-2021-20028 to the Known Exploited Vulnerabilities catalog on 2022-03-28, which means the agency holds evidence of exploitation in the wild; US federal civilian agencies had to remediate it by 2022-04-18 under BOD 22-01. CISA flags the vulnerability as one used in known ransomware campaigns. Weaponised exploit code for CVE-2021-20028 is publicly available. 1 public proof-of-concept repository is tracked for this identifier. It currently carries a trending score of 48 in the Threadlinqs vulnerability feed.

- [trickest/cve](https://github.com/trickest/cve/blob/main/2021/CVE-2021-20028.md) (trickest)

## Affected products and versions

- [SonicWall](https://intel.threadlinqs.com/vendors/sonicwall): SRA/SMA100

## How to fix CVE-2021-20028

Because CVE-2021-20028 is KEV-listed, US federal civilian agencies were required to apply the vendor fix, or stop using the product, by 2022-04-18. No vendor patch reference has been recorded for CVE-2021-20028 in the tracked sources. Follow the references below for a fix, and treat the products listed above as exposed until the vendor states otherwise.

## Threat activity tracking CVE-2021-20028

1 tracked threat in the Threadlinqs corpus references CVE-2021-20028, either in the campaign’s CVE list or as an indicator on the campaign record.

- [Coordinated Reconnaissance Campaign Maps SonicWall SSL VPN Attack Surface via Commercial Proxy Infrastructure (84,142 Sessions / 4,305 IPs / 20 ASNs)](https://intel.threadlinqs.com/threat/TL-2026-1468) — HIGH · 2026-02-25

## Sources

Enriched from CVE.org, FIRST EPSS, CISA KEV, GitHub Security Advisories, public proof-of-concept repositories. Last verified by Threadlinqs on 2026-10-10.

**Vendor advisory and patch**

- [psirt.global.sonicwall.com](https://psirt.global.sonicwall.com/vuln-detail/SNWLID-2021-0017)

Canonical: https://intel.threadlinqs.com/cve/CVE-2021-20028
Full detection coverage and IOCs for threats exploiting CVE-2021-20028 via the Threadlinqs MCP server (Purple tier): https://intel.threadlinqs.com/mcp