CVE-2021-20041Network attack vector

Unauthenticated CPU exhaustion via infinite HTTP request loop

Published Dec 8, 2021 · Updated Aug 3, 2024

Infinite-loop denial of service in SonicWall Secure Mobile Access 100 Series allows remote attackers to exhaust CPU via crafted HTTP requests. The /fileshare/sonicfiles/sonicfiles handler enters a loop whose exit condition cannot be reached while processing the crafted request. The affected branches are 9.0.0.11-31sv and earlier, 10.2.0.8-37sv and earlier, 10.2.1.1-19sv and earlier, and 10.2.1.2-24sv and earlier; no authentication is required.

CVSS severity7.5
High
EPSS probability6.60%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Infinite-loop denial of service in SonicWall Secure Mobile Access 100 Series allows remote attackers to exhaust CPU via crafted HTTP requests. The /fileshare/sonicfiles/sonicfiles handler enters a loop whose exit condition cannot be reached while processing the crafted request. The affected branches are 9.0.0.11-31sv and earlier, 10.2.0.8-37sv and earlier, 10.2.1.1-19sv and earlier, and 10.2.1.2-24sv and earlier; no authentication is required.

The record

CVE
CVE-2021-20041
Published
Dec 8, 2021
Updated
Aug 3, 2024
Vendor
SonicWall
Product
Secure Mobile Access (SMA) 100 Series
Classifications
CWE-835, T1499.004
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

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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 NVDCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
7.8NIST NVDAV:N/AC:L/Au:N/C:N/I:N/A:C

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 9, 2026Sep 15, 2026
Latest reporting daySep 15, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-835Loop with Unreachable Exit Condition ('Infinite Loop')
T1499.004Endpoint Denial of Service: Application or System Exploitation

Public exploit references

No public exploit references are available in this record.

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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