{"cve":"CVE-2021-20134","nvd":{"published":"2021-12-30T22:15:08.460","modified":"2026-06-17T03:33:19.840","status":"Modified","description":"Quagga Services on D-Link DIR-2640 less than or equal to version 1.11B02 are affected by an absolute path traversal vulnerability that allows a remote, authenticated attacker to set an arbitrary file on the router's filesystem as the log file used by either Quagga service (zebra or ripd). Subsequent log messages will be appended to the file, prefixed by a timestamp and some logging metadata. Remote code execution can be achieved by using this vulnerability to append to a shell script on the router's filesystem, and then awaiting or triggering the execution of that script. A remote, unauthenticated root shell can easily be obtained on the device in this fashion.","cvss_v4":null,"cvss_v3":{"version":"3.1","vector":"CVSS:3.1/AV:A/AC:L/PR:H/UI:N/S:C/C:H/I:H/A:H","score":8.4},"cwes":["CWE-22"],"references":["https://www.tenable.com/security/research/tra-2021-44","https://www.tenable.com/security/research/tra-2021-44"],"products":["dlink:dir-2640-us_firmware"],"source":"nvd","synced_at":"2026-10-19T21:26:33.761856376+00:00"},"epss":{"cve":"CVE-2021-20134","score":0.07774,"percentile":0.94647,"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."]}