SonicWall SSLVPN SMA100 SQL Injection Vulnerability (CVE-2021-20016)
Published In CISA KEV since Sources: SingCERT, CVE.org
- Actively exploited
- Source: ANSSI / CERT-FR, CSA/SingCERT How we classify
- Ransomware
What is affected, what to do
A SQL-Injection vulnerability in the SonicWall SSLVPN SMA100 product allows a remote unauthenticated attacker to perform SQL query to access username password and other session related information. This vulnerability impacts SMA100 build version 10.x.
The vulnerability is being actively exploited; treat it as a priority. CISA lists it as used in ransomware campaigns. The available sources name no fixed version. Check the vendor guidance in the references below. Immediate actions, mitigation and detection rules are in the runbook below.
- Affected
- SonicWall SMA100
eq SMA100 build version 10.x..SMA100 build version 10.x
- SonicWall SMA100
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Metrics
9.8
Priority
XIEM Effective CVSS: highest available CVSS rating from NVD and vendor data.
Source: NVD, CVSS v3
9.8
CVSS v3
Severity Critical on the scale from 0 to 10.
Source: SingCERT, CVE.org
40.0 %
EPSS score
Elevated — model estimates 10-50% exploitation likelihood.
Source: FIRST EPSS, percentile 98.6
Show all metrics
- Severity
- Critical
Priority (0–325)
The priority score is a consolidated metric that condenses several individual signals into a single, action-guiding ranking: technical severity (CVSS), exploitation likelihood (EPSS), known-exploited status (KEV) and the context of the affected asset. The aim is to answer the only truly important question in vulnerability management: what first?
Read in glossary- 251.82 Methodology
Exploit maturity
An exploit is code or a technique that specifically uses a concrete vulnerability to force unintended behaviour — such as executing code or escalating privileges. It is the tool that turns a theoretical flaw into a practical attack.
Read in glossary- actively exploitedSource: ANSSI / CERT-FR, CSA/SingCERT How we classify
XIEM Effective CVSS
XIEM® is the tiered managed-security operating model from NEOSEC and a registered trademark of NEOSEC GmbH. It extends classic SIEM — the central collection, normalisation and correlation of security-relevant events — with endpoint forensics, network visibility and deception technology, and consolidates them into three building tiers: Sentry, Orchestrate and Command.
Read in glossary- 9.8 Methodology
CVSS v3
CVSS is the globally established, open standard for assessing the technical severity of a vulnerability on a scale from 0 to 10. It describes how easily a flaw can be exploited and what damage it can cause — but not how likely its actual exploitation is. CVSS and the complementary EPSS deliberately answer different questions.
Read in glossary- 9.8
EPSS score
The EPSS score is the absolute model output for an individual vulnerability: the estimated probability of real-world exploitation within the next 30 days, expressed as a value between 0 and 1 (i.e. 0 % to 100 %). A score of 0.42 means „the model estimates a 42 % chance of real-world exploitation within 30 days“.
Read in glossary- 40.0 %
- Elevated — model estimates 10-50% exploitation likelihood.
EPSS percentile
The EPSS percentile is the relative position of a vulnerability within all EPSS-scored CVEs, expressed as a value between 0 and 1. A percentile of 0.90 means „this CVE has a higher EPSS score than 90 % of all other scored CVEs“. Unlike the EPSS score, it is not a probability — but a positioning within a ranking.
Read in glossary- 98.6
- Critical — this CVE ranks in the top fifth of all CVEs scored today (rank ≥ 80%).
KEV status
The KEV catalogue is a list maintained by the US authority CISA of vulnerabilities for which active exploitation in the wild has been confirmed. It answers not the question „how severe?“ but „is it already being attacked?“ — thereby sharply prioritising patching.
Read in glossary- Actively exploited
- Published
In CISA KEV since
The KEV catalogue is a list maintained by the US authority CISA of vulnerabilities for which active exploitation in the wild has been confirmed. It answers not the question „how severe?“ but „is it already being attacked?“ — thereby sharply prioritising patching.
Read in glossary- CISA assessment (SSVC)
- Exploitation: active · automatable · Technical impact: total
- Source: CISA Vulnrichment, as of 5 February 2021
CWE
CWE is a catalogue of typical weakness types in software and hardware — such as flawed input validation, unsafe memory handling or poor authentication. Where a CVE names a concrete vulnerability in a concrete product, a CWE describes the underlying class of defect.
Read in glossary- CWE-89
Response and mitigation
Why act now?
Prioritisation rationale
This flaw is network-reachable without authentication or user interaction. It hands the attacker valid credentials and sessions for remote access, which makes it an ideal initial-access vector. CISA explicitly flags it as used in ransomware campaigns, and it ranks among the CVEs most likely to be exploited. Typical victims are mid-market firms and critical-infrastructure operators that rely on the SMA 100 as their primary SSL VPN. Any internet-facing SMA running affected 10.x firmware should be handled as an emergency (top priority). A credential reset remains mandatory even after patching, because exploitation leaves no trace on endpoints.
Runbook step 1
Immediate response (0-24 h)
- Inventory and version check: Identify every SonicWall SMA 100 series appliance (SMA 200, 210, 400, 410, SMA 500v) and confirm its firmware. The 10.x branch from 10.0.0.0 through 10.2.0.5-d-29sv is affected. A patch is available from the vendor — look up the fixed firmware build in the SonicWall PSIRT advisory and deploy it immediately.
- Shrink exposure now: Until patched, remove the SMA web/portal interface from the internet or restrict it to known source ranges with an upstream firewall ACL on HTTPS. The management interface must never be internet-reachable.
- Treat credentials as compromised: The flaw exposes usernames, passwords and session data. Reset every account that authenticates via the SMA: the local user database, admin accounts, and AD/LDAP accounts used through the portal. Start with privileged accounts.
- Kill active sessions: Terminate all existing SSL-VPN sessions so stolen session tokens become useless, then force re-authentication.
- Enforce MFA: Require multi-factor authentication (TOTP or email OTP) on the SMA for all users. This neutralises harvested passwords for VPN access.
- Start compromise assessment: Preserve appliance logs and VPN login history before a reboot or upgrade overwrites them. Treat internal IPs assigned via the SMA since disclosure as potentially hostile.
Runbook step 2
Mitigation layers
- Network segmentation: Put VPN client pools in a dedicated segment. Allow east-west access from it to domain controllers (LDAP/Kerberos/SMB), hypervisor management and backup infrastructure on a least-privilege basis only. This slows lateral movement after credential theft.
- WAF/IPS: Enable generic SQL-injection signatures in front of the SMA (e.g. Suricata/Snort
web-application-attack/sql-injectioncategories). Add a custom rule for HTTP requests to the SMA portal that contain SQL metacharacters or keywords (UNION,SELECT,' OR,--,/*,SLEEP() in the URI, parameters or body. Where available, enable vendor signatures for CVE-2021-20016 on the upstream NGFW. - IAM/least privilege: Never use domain-admin-level accounts for VPN access. Exclude service and admin accounts from SSL-VPN login. Apply geo-IP or country restrictions on VPN authentication.
- Configuration hardening: Disable unused portal features and bookmarks. Forward logs via remote syslog to a central SIEM so evidence survives an appliance compromise.
- Lifecycle management: Track SMA appliances in vulnerability management with a tight patch SLA (perimeter devices ≤ 72 h). Retire unsupported firmware branches.
Runbook step 3
Detection rules
- Web requests to the SMA (appliance log/reverse proxy): Look for portal requests carrying SQL-injection patterns. Example SPL:
index=vpn sourcetype=sonicwall:sma (uri="*UNION*" OR uri="*SELECT*" OR uri="*%27*" OR uri="*SLEEP(*"). Sigma shape:logsource: webserver,selection: cs-uri-query|contains: ["UNION", "SELECT", "' OR", "SLEEP("], scoped to the SMA host. - Anomalous VPN logins: Flag successful logins from unusual countries or hosting/VPS ASNs, impossible travel, or multiple accounts from one source IP in a short window. KQL idea:
SonicWallLogs | where Action == "login success" | summarize dcount(User) by SrcIP, bin(TimeGenerated, 1h) | where dcount_User > 3. - Follow-on activity from the VPN pool (Windows): Watch Event ID 4624 (logon type 3/10) and 4625 from VPN-pool IPs against servers and DCs, Event ID 4768/4769 with RC4 encryption (Kerberoasting), and 4672 privileged logons sourced from the VPN segment.
- Network telemetry (Zeek/Suricata): Alert on SMB/RDP/WinRM sweeps from the VPN pool (
conn.log: one source → > 50 destinations on 445/3389/5985 within 10 min) and large outbound transfers indicating pre-encryption exfiltration. - EDR process chains: On hosts reached via VPN sessions, hunt for
vssadmin delete shadows,wbadmin delete,bcdedit /set recoveryenabled no, PsExec or remote service creation (Sysmon EID 1, Windows EID 7045), and mass file renames — classic ransomware precursors.
- Web requests to the SMA (appliance log/reverse proxy): Look for portal requests carrying SQL-injection patterns. Example SPL:
Detection rules
No NEOSEC detection rule is available for this vulnerability yet.
Classification under NIS2 and CRA
Rule-based classification from exploitation status and severity. It does not replace a case-by-case assessment.
NIS2
NIS2 is EU Directive (EU) 2022/2555 to raise the level of cybersecurity across the Union. It substantially broadens obligations compared with the first NIS directive: more sectors, mandatory risk management, staged reporting duties and personal accountability of senior management.
Read in glossary- Actively exploited: treat the vulnerability as a priority in vulnerability handling under Art. 21(2)(e) NIS2. If it is exploited in your environment, check the reporting obligation under Art. 23 (early warning within 24 hours).
CRA
The CRA is EU Regulation (EU) 2024/2847 setting horizontal cybersecurity requirements for „products with digital elements“ — from industrial controllers and software to connected consumer devices. For the first time manufacturers must ensure security across the entire product lifecycle, handle vulnerabilities and provide security updates.
Read in glossary- Since 11.09.2026, manufacturers of affected products with digital elements must report actively exploited vulnerabilities under Art. 14 CRA, with an early warning within 24 hours via ENISA's single reporting platform.
ISO/IEC 27001
ISO/IEC 27001 is the internationally leading standard for an information security management system (ISMS). It describes a risk-based, process-oriented framework to systematically plan, implement, review and improve information security.
Read in glossary- Control A.8.8, management of technical vulnerabilities: assess relevance to your systems, plan remediation and keep evidence.
Description
A SQL-Injection vulnerability in the SonicWall SSLVPN SMA100 product allows a remote unauthenticated attacker to perform SQL query to access username password and other session related information. This vulnerability impacts SMA100 build version 10.x.
Source: CSA/SingCERT, CISA KEV Catalog, cvelistv5, NVD (NIST)
Affected products
The following versions are affected. Older releases of the same product line are also vulnerable unless stated otherwise.
| Affected versions | Fixed in | ||
|---|---|---|---|
| SonicWall | SonicWall SMA100 |
|
|
| sonicwall | sma_500v |
|
|
Vendors and products
Affected operating systems
| Other | sonicwall | sma_100_firmware | — |
| Other | sonicwall | sma_200_firmware | — |
| Other | sonicwall | sma_210_firmware | — |
| Other | sonicwall | sma_400_firmware | — |
| Other | sonicwall | sma_410_firmware | — |
Weakness classes (CWE)
CWE-89Improper Neutralization of Special Elements used in an SQL Command ('SQL Injection')
Base
The product constructs all or part of an SQL command using externally-influenced input from an upstream component, but it does not neutralize or incorrectly neutralizes special elements that could modify the intended SQL command when it is sent to a downstream component. Without sufficient removal or quoting of SQL syntax in user-controllable inputs, the generated SQL query can cause those inputs to be interpreted as SQL instead of ordinary user data.
Entry at MITRE CWE-89
Public exploit references
Publicly reported proof-of-concepts, exploit modules and detection templates for this vulnerability. NEOSEC links to the original sources only and does not provide any exploit code.
| CISA KEV Catalog | CISA Known Exploited Vulnerability (opens in a new tab)cisa.gov | actively exploited | |
| CSA/SingCERT | [Update] Probable Vulnerabilities Exploited in some SonicWall Secure Remote Access Products (opens in a new tab)CSA/SingCERT | actively exploited | |
| ANSSI / CERT-FRLicence Ouverte 2.0, as of | CERTFR-2021-ALE-001 – |MàJ] Vulnérabilité dans SonicWall SMA100 (clôturée 2021-05-12) (opens in a new tab)cert.cyber.gouv.fr | actively exploited |
References & sources
- psirt.global.sonicwall.comvuln-detail/SNWLID-2021-0001x_refsource_CONFIRM
- cisa.govknown-exploited-vulnerabilities-catalog?field_cve=CVE-2021-20016government-resource
- cert.cyber.gouv.frANSSI / CERT-FR: CERTFR-2021-ALE-001 – |MàJ] Vulnérabilité dans SonicWall SMA100 (clôturée 2021-05-12)cert-fr
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<a href="https://intel.neosec.eu/en/cve/CVE-2021-20016"><img src="https://intel.neosec.eu/badge/cve/CVE-2021-20016.svg?lang=en" alt="CVE-2021-20016 – NEOSEC Intel" height="20"></a>