CVE-2021-20134

Root code execution via arbitrary log-file append

Published Dec 30, 2021 · Updated Aug 3, 2024

Absolute path traversal in Quagga services on D-Link DIR-2640 1.11B02 and earlier allows remote authenticated users to execute code as root. The Quagga configuration terminal accepts an absolute log-file path and appends logmsg text to that file without restricting the destination. Access to the zebra or ripd configuration interface and execution of the modified shell script are required; successful exploitation runs commands with router root privileges.

CVSS severity8.4
High
EPSS probability7.53%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Absolute path traversal in Quagga services on D-Link DIR-2640 1.11B02 and earlier allows remote authenticated users to execute code as root. The Quagga configuration terminal accepts an absolute log-file path and appends logmsg text to that file without restricting the destination. Access to the zebra or ripd configuration interface and execution of the modified shell script are required; successful exploitation runs commands with router root privileges.

The record

CVE
CVE-2021-20134
Published
Dec 30, 2021
Updated
Aug 3, 2024
Vendor
D-Link
Product
DIR-2640
Classifications
CWE-22, T1059.004
Attack vector
adjacent
Privileges
authenticated

Timeline

How it unfolded

  1. Dec 30, 2021CVE publishedPublication date reported by the CVE source.
  2. Aug 3, 2024Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

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Is a vulnerable build present?

Compare these published version ranges with your installed build and any vendor patches.

  1. Affected versionversion=<= 1.11B02

What conditions does exploitation require?

Attack vectoradjacent
Required privilegesauthenticated

What is affected?

D-Link · DIR-2640version=<= 1.11B02

Published CVSS scores

7.4NVDAV:A/AC:M/Au:S/C:C/I:C/A:C
8.4NVDCVSS:3.1/AV:A/AC:L/PR:H/UI:N/S:C/C:H/I:H/A:H

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

Daily unique IPsNo honeypot observations are available for this CVE in the selected window.

No observations available

Sep 10, 2026Sep 16, 2026
Latest reporting daySep 16, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectoradjacent
Privilegesauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-22Improper Limitation of a Pathname to a Restricted Directory ('Path Traversal')
T1059.004Command and Scripting Interpreter: Unix Shell

Public exploit references

No public exploit references are available in this record.

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Technologies

Your stack

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Your stack

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