CVE-2021-21817Public exploitNetwork attack vector

Arbitrary file disclosure via Zebra login banner

Published Jul 16, 2021 · Updated Aug 3, 2024

Information disclosure in D-Link DIR-3040 firmware 1.13B03 and earlier allows remote attackers to read arbitrary files over TCP port 2601. The default Zebra service lets an unauthenticated client set the login banner source to an arbitrary file path, then returns that file when a new session connects. Any network host that can reach the service can retrieve files such as /etc/passwd, exposing stored credentials and other router data without modifying file contents.

CVSS severity7.5
High
EPSS probability2.01%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Information disclosure in D-Link DIR-3040 firmware 1.13B03 and earlier allows remote attackers to read arbitrary files over TCP port 2601. The default Zebra service lets an unauthenticated client set the login banner source to an arbitrary file path, then returns that file when a new session connects. Any network host that can reach the service can retrieve files such as /etc/passwd, exposing stored credentials and other router data without modifying file contents.

The record

CVE
CVE-2021-21817
Published
Jul 16, 2021
Updated
Aug 3, 2024
Vendor
D-Link
Product
DIR-3040
Classifications
CWE-200, T1005
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Jul 16, 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=D-LINK DIR-3040 1.13B03

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

D-Link · DIR-3040version=D-LINK DIR-3040 1.13B03

Published CVSS scores

7.5NIST NVDCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N
7.5Cisco TalosCVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N
5.0NIST NVDAV:N/AC:L/Au:N/C:P/I:N/A:N

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)
Vectornetwork
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitPublished

Weakness, pattern, technique

CWE-200Exposure of Sensitive Information to an Unauthorized Actor
T1005Data from Local System

Public exploit references

Labels summarize the accepted research assessment. They do not indicate a test against your environment.

Technologies

Your stack

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Your stack

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