CVE-2021-20042Public exploitNetwork attack vector

Firewall bypass via pre-authentication sonicfiles proxying

Published Dec 8, 2021 · Updated Aug 3, 2024

Confused-deputy behavior in SonicWall SMA 100 firmware allows remote attackers to bypass firewall rules through crafted HTTPS requests. The sonicfiles component invokes fileexplorer for RacNumber 25 before validating the authentication cookie, while its destination allowlist check is disabled. The blind proxy can map internal TCP services and make SMB requests; reading or writing SMB data still requires valid credentials or guest access.

CVSS severity9.8
Critical
EPSS probability2.59%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Confused-deputy behavior in SonicWall SMA 100 firmware allows remote attackers to bypass firewall rules through crafted HTTPS requests. The sonicfiles component invokes fileexplorer for RacNumber 25 before validating the authentication cookie, while its destination allowlist check is disabled. The blind proxy can map internal TCP services and make SMB requests; reading or writing SMB data still requires valid credentials or guest access.

The record

CVE
CVE-2021-20042
Published
Dec 8, 2021
Updated
Aug 3, 2024
Vendor
SonicWall
Product
Secure Mobile Access (SMA) 100 Series
Classifications
CWE-441, T1090, T1046
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Dec 8, 2021CVE publishedPublication date reported by the CVE source.
  2. Aug 3, 2024Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

Compare your product and version with the public record. A matching version still requires validation against your environment.

Is a vulnerable build present?

Compare these published version ranges with your installed build and any vendor patches.

  1. Affected versionversion=10.2.0.8-37sv and earlier
  2. Affected versionversion=10.2.1.1-19sv and earlier
  3. Affected versionversion=10.2.1.2-24sv and earlier
  4. Affected versionversion=9.0.0.11-31sv and earlier

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

SonicWall · Secure Mobile Access (SMA) 100 Seriesversion=10.2.0.8-37sv and earlier; version=10.2.1.1-19sv and earlier; version=10.2.1.2-24sv and earlier; version=9.0.0.11-31sv and earlier

Published CVSS scores

7.5NIST NVDAV:N/AC:L/Au:N/C:P/I:P/A:P
9.8NIST NVDCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

Daily unique IPsNo honeypot observations are available for this CVE in the selected window.

No observations available

Sep 10, 2026Sep 16, 2026
Latest reporting daySep 16, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitPublished

Weakness, pattern, technique

CWE-441Unintended Proxy or Intermediary ('Confused Deputy')
T1090Proxy
T1046Network Service Discovery

Public exploit references

Labels summarize the accepted research assessment. They do not indicate a test against your environment.

Technologies

Your stack

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Your stack

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