CVE-2021-40127

Cisco Small Business 200, 300, and 500 Series Switches Web-Based Management Interface Denial of Service Vulnerability

MEDIUM
5.3
CVSS Score
Published: November 4, 2021 at 03:30 PM UTC
Updated: June 17, 2026 at 04:06 AM UTC
133 products affected across 1 vendorSg300-10pp FirmwareSg300-28mp FirmwareSf300-48pp Firmware

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Severity
MEDIUM5.3
Exploit prediction
EPSS 1%
SSVC
No known exploit

Description

A vulnerability in the web-based management interface of Cisco Small Business 200 Series Smart Switches, Cisco Small Business 300 Series Managed Switches, and Cisco Small Business 500 Series Stackable Managed Switches could allow an unauthenticated, remote attacker to render the web-based management interface unusable, resulting in a denial of service (DoS) condition. This vulnerability is due to improper validation of HTTP requests. An attacker could exploit this vulnerability by sending a crafted HTTP request to an affected device. A successful exploit could allow the attacker to cause a permanent invalid redirect for requests sent to the web-based management interface of the device, resulting in a DoS condition.

Affected

Our own answer: ranges merged, affected separated from platform-only, with confidence and review flags.

All versions
cisco-sf200-24 (same device)
All versions
cisco-sf200-24fp (same device)
All versions
cisco-sf200-24p (same device)
All versions
cisco-sf200-48 (same device)
All versions
cisco-sf200-48p (same device)
All versions
cisco-sf200e-24 (same device)
All versions
cisco-sf200e-24p (same device)
All versions
cisco-sf200e-48 (same device)
All versions
cisco-sf200e-48p (same device)
cisco-sf300-08 (same device)

Remediation

No guide yet

No remediation guidance has been written for this CVE yet. What the record does show:

SSVC — Action Prioritization

SSVCNo known exploitAutomatablePartial impact

SSVC signals action urgency (what to patch first), separate from CVSS which measures severity.

CVSS

5.3MEDIUMcisco
Attack Vector
NETWORK
Complexity
LOW
Privileges
NONE
User Interaction
NONE
Scope
UNCHANGED
Confidentiality
NONE
Integrity
NONE
Availability
LOW
Vector?

Quick Info

StatusMODIFIED
CWE
CWE-20

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