{"cve":"CVE-2020-13364","nvd":{"published":"2020-08-06T17:15:10.830","modified":"2026-06-17T02:53:01.923","status":"Modified","description":"A backdoor in certain Zyxel products allows remote TELNET access via a CGI script. This affects NAS520 V5.21(AASZ.4)C0, V5.21(AASZ.0)C0, V5.11(AASZ.3)C0, and V5.11(AASZ.0)C0; NAS542 V5.11(ABAG.0)C0, V5.20(ABAG.1)C0, and V5.21(ABAG.3)C0; NSA325 v2_V4.81(AALS.0)C0 and V4.81(AAAJ.1)C0; NSA310 4.22(AFK.0)C0 and 4.22(AFK.1)C0; NAS326 V5.21(AAZF.8)C0, V5.11(AAZF.4)C0, V5.11(AAZF.2)C0, and V5.11(AAZF.3)C0; NSA310S V4.75(AALH.2)C0; NSA320S V4.75(AANV.2)C0 and V4.75(AANV.1)C0; NSA221 V4.41(AFM.1)C0; and NAS540 V5.21(AATB.5)C0 and V5.21(AATB.3)C0.","cvss_v4":null,"cvss_v3":{"version":"3.1","vector":"CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H","score":8.8},"cwes":[],"references":["https://www.zyxel.com/support/Zyxel-security-advisory-for-NAS-remote-access-vulnerability.shtml","https://www.zyxel.com/us/en/support/security_advisories.shtml","https://www.zyxel.com/support/Zyxel-security-advisory-for-NAS-remote-access-vulnerability.shtml","https://www.zyxel.com/us/en/support/security_advisories.shtml"],"products":["zyxel:nas326_firmware","zyxel:nas520_firmware","zyxel:nas540_firmware","zyxel:nas542_firmware"],"source":"nvd","synced_at":"2026-10-19T21:06:22.076270124+00:00"},"epss":{"cve":"CVE-2020-13364","score":0.01151,"percentile":0.66947,"date":"2026-10-31"},"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."]}