{"id":"CVE-2021-1534","url":"https://www.cyber-defence.io/tools/cve/CVE-2021-1534","generatedAt":"2026-10-28T02:57:43.250Z","title":"A vulnerability in the antispam protection mechanisms of Cisco AsyncOS Software for Cisco Email Security Appliance (ESA) could allow an unauthenticated, remote attacker to bypass the URL reputation filters on an affected device.","description":"A vulnerability in the antispam protection mechanisms of Cisco AsyncOS Software for Cisco Email Security Appliance (ESA) could allow an unauthenticated, remote attacker to bypass the URL reputation filters on an affected device. This vulnerability is due to improper processing of URLs. An attacker could exploit this vulnerability by crafting a URL in a particular way. A successful exploit could allow the attacker to bypass the URL reputation filters that are configured for an affected device, which could allow malicious URLs to pass through the device.","published":"2021-10-06T20:15:08.000Z","lastModified":"2026-06-17T03:32:00.000Z","status":"Modified","sourceIdentifier":"psirt@cisco.com","cvss":{"version":"3.1","score":5.3,"severity":"MEDIUM","vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:N"},"cwe":["CWE-20"],"affected":["cisco/asyncos"],"epss":{"score":0.01067,"percentile":0.64544,"date":"2026-10-26","history":[]},"kev":{"listed":false},"exploits":{"count":0,"verified":false,"firstPublished":null,"source":"Exploit-DB (https://gitlab.com/exploit-database/exploitdb)","entries":[]},"verdict":{"level":"low","text":"Lower severity and a low EPSS score (1.07%). Track it; it rarely justifies an emergency change on its own."},"changes":[],"references":[{"url":"https://tools.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-esa-url-bypass-sGcfsDrp","tags":["Vendor Advisory"],"source":"psirt@cisco.com"},{"url":"https://tools.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-esa-url-bypass-sGcfsDrp","tags":["Vendor Advisory"],"source":"af854a3a-2127-422b-91ae-364da2661108"}],"sources":{"nvd":"https://nvd.nist.gov/vuln/detail/CVE-2021-1534","epss":"https://www.first.org/epss/","kev":"https://www.cisa.gov/known-exploited-vulnerabilities-catalog","exploitdb":"https://www.exploit-db.com/"},"licence":"CC BY 4.0 — link back to the CVE Explorer if you publish the results; upstream data remains subject to its own terms."}