{"cve":"CVE-2021-40127","nvd":{"published":"2021-11-04T16:15:09.643","modified":"2026-06-17T04:06:34.437","status":"Modified","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.","cvss_v4":null,"cvss_v3":{"version":"3.1","vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L","score":5.3},"cwes":["CWE-20"],"references":["https://tools.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-smb-switches-web-dos-xMyFFkt8","https://tools.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-smb-switches-web-dos-xMyFFkt8"],"products":["cisco:sf200-24_firmware","cisco:sf200-24fp_firmware","cisco:sf200-24p_firmware","cisco:sf200-48_firmware","cisco:sf200-48p_firmware","cisco:sf200e-24_firmware","cisco:sf200e-24p_firmware","cisco:sf200e-48_firmware","cisco:sf200e-48p_firmware","cisco:sf300-08_firmware","cisco:sf300-24_firmware","cisco:sf300-24mp_firmware","cisco:sf300-24p_firmware","cisco:sf300-24pp_firmware","cisco:sf300-48_firmware","cisco:sf300-48p_firmware","cisco:sf300-48pp_firmware","cisco:sf302-08_firmware","cisco:sf302-08mp_firmware","cisco:sf302-08mpp_firmware","cisco:sf302-08p_firmware","cisco:sf302-08pp_firmware","cisco:sf500-24_firmware","cisco:sf500-24mp_firmware","cisco:sf500-24p_firmware","cisco:sf500-48_firmware","cisco:sf500-48mp_firmware","cisco:sf500-48p_firmware","cisco:sg200-08_firmware","cisco:sg200-08p_firmware","cisco:sg200-10fp_firmware","cisco:sg200-18_firmware","cisco:sg200-26_firmware","cisco:sg200-26fp_firmware","cisco:sg200-26p_firmware","cisco:sg200-50_firmware","cisco:sg200-50fp_firmware","cisco:sg200-50p_firmware","cisco:sg300-10_firmware","cisco:sg300-10mp_firmware","cisco:sg300-10mpp_firmware","cisco:sg300-10p_firmware","cisco:sg300-10pp_firmware","cisco:sg300-20_firmware","cisco:sg300-28_firmware","cisco:sg300-28mp_firmware","cisco:sg300-28p_firmware","cisco:sg300-28pp_firmware","cisco:sg300-28sfp_firmware","cisco:sg300-52_firmware"],"source":"nvd","synced_at":"2026-10-19T21:24:39.218183596+00:00"},"epss":{"cve":"CVE-2021-40127","score":0.01281,"percentile":0.70034,"date":"2026-11-01"},"kev":null,"osv":[],"attribution":["This product uses the NVD API but is not endorsed or certified by the NVD.","EPSS scores: FIRST Exploit Prediction Scoring System, https://www.first.org/epss","Known exploited vulnerabilities: CISA Known Exploited Vulnerabilities Catalog, https://www.cisa.gov/known-exploited-vulnerabilities-catalog","Package advisories: OSV (https://osv.dev), from the GitHub Advisory Database, PyPA, Go, RustSec and other ecosystem databases, under CC-BY 4.0 or CC0","CVE records: the CVE Program's CVE List (https://www.cve.org), under its terms of use (https://www.cve.org/Legal/TermsOfUse). CVE is a registered trademark of The MITRE Corporation; this product is not affiliated with the CVE Program."]}