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Vulnerability record · CVE-2021-20134 · published 30 December 2021

CVE-2021-20134: Dlink dir-2640-us firmware path traversal vulnerability

Dlink · Dir 2640 Us Firmware

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.

8.4 CVSS 3.1 High EPSS 7.5% · top 5.7% CWE-22 · Path traversal
8.4CVSS 3.1 base score, v2 7.4
7.5%EPSS exploitation probability, 30 days
NoNot in CISA KEV
1Affected product versions listed by NVD
2References, 2 tagged exploit
17 Jun 2026Last modified by NVD

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:3.1/AV:A/AC:L/PR:H/UI:N/S:C/C:H/I:H/A:H

Affected products

1 vulnerable configurations from NVD's CPE data, grouped by vendor and product.

References

LinkTags
https://www.tenable.com/security/research/tra-2021-44 ExploitThird Party Advisory
https://www.tenable.com/security/research/tra-2021-44 ExploitThird Party Advisory

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Related vulnerabilities

Same products first, then exploited flaws of the same weakness class.

8.8CVE-2021-20132Dlink dir-2640-us firmware hard-coded credentials vulnerabilityQuagga Services on D-Link DIR-2640 less than or equal to version 1.11B02 use default hard-coded credentials, which can allow a remote attacker to gai…EPSS 4.3%8.1CVE-2021-34203Dlink dir-2640-us firmware insecure default initialization vulnerabilityD-Link DIR-2640-US 1.01B04 is vulnerable to Incorrect Access Control. Router ac2600 (dir-2640-us), when setting PPPoE, will start quagga process in t…EPSS 1.2%7.8CVE-2021-34202Dlink dir-2640-us firmware out-of-bounds write vulnerabilityThere are multiple out-of-bounds vulnerabilities in some processes of D-Link AC2600(DIR-2640) 1.01B04. Ordinary permissions can be elevated to admini…EPSS 3.6%7.1CVE-2021-34201Dlink dir-2640-us firmware out-of-bounds write vulnerabilityD-Link DIR-2640-US 1.01B04 is vulnerable to Buffer Overflow. There are multiple out-of-bounds vulnerabilities in some processes of D-Link AC2600(DIR-…EPSS 0.54%6.8CVE-2021-34204Dlink dir-2640-us firmware insufficiently protected credentials vulnerabilityD-Link DIR-2640-US 1.01B04 is affected by Insufficiently Protected Credentials. D-Link AC2600(DIR-2640) stores the device system account password in …EPSS 1.1%6.1CVE-2021-20133Dlink dir-2640-us firmware path traversal vulnerabilityQuagga 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 remot…EPSS 2.1%9.8CVE-2026-93616Checkpoint multi-domain security management path traversal vulnerabilityA directory traversal and file upload vulnerability allows an unauthenticated attacker to upload and execute arbitrary scripts on Check Point Managem…KEVEPSS 20%10.0CVE-2026-85706GitLab CE/EE repository commits API path traversal allows unauthenticated file readGitLab CE/EE contains improper path confinement and missing authentication enforcement in the repository commits API, allowing an unauthenticated use…KEVEPSS 91%analysed

Source: NIST National Vulnerability Database (record CVE-2021-20134), CISA KEV, FIRST EPSS (scores of 2026-09-26). This page is refreshed as NVD updates the record.