{"cve":"CVE-2021-21739","nvd":{"published":"2021-08-05T20:15:07.703","modified":"2026-06-17T03:36:04.173","status":"Modified","description":"A ZTE's product of the transport network access layer has a security vulnerability. Because the system does not sufficiently verify the data reliability, attackers could replace an authenticated optical module on the equipment with an unauthenticated one, bypassing system authentication and detection, thus affecting signal transmission. This affects: <ZXCTN 6120H><V5.10.00B24>","cvss_v4":null,"cvss_v3":{"version":"3.1","vector":"CVSS:3.1/AV:P/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N","score":4.6},"cwes":["CWE-345"],"references":["https://support.zte.com.cn/support/news/LoopholeInfoDetail.aspx?newsId=1017024","https://support.zte.com.cn/support/news/LoopholeInfoDetail.aspx?newsId=1017024"],"products":["zte:zxctn_6120h_firmware"],"source":"nvd","synced_at":"2026-10-19T21:21:13.713336758+00:00"},"epss":{"cve":"CVE-2021-21739","score":0.00248,"percentile":0.16188,"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."]}