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NVD / CVE Program· CNA talos

CVE-2021-21816: An information disclosure vulnerability exists in the Syslog functionality of D-LINK DIR-3040 1.13B03.

MediumCVSS 4.3 · v3.1—Proof of concept No fix recorded

Noroxi assessment

Priority: Monitor (action score 27/100)

  • A ready-made attack module is public (Nuclei); exploiting it takes no special expertise.
  • Public proof-of-concept code exists (Exploit-DB / GitHub); there is no record of exploitation in the wild.
  • Probability of exploitation in the next 30 days: 32.3% (FIRST EPSS); higher than 98.3% of all records.
  • Anyone who can reach it over the internet can trigger it. No account or password is required. A user must open a link or visit a page. No special conditions are required; it is repeatable.
  • According to the record, no fixed version is available yet.
  • Severity is disputed: the assigning authority (CNA) scores it 6.5, NVD 4.3.

Low priority for now. Update when a fix is released; follow the vendor's advisory.

Generated automatically from the record's data: CVSS (NVD and CNA), CISA KEV and SSVC, FIRST EPSS, exploit sources, fixed versions. How we calculate it

Primary sources: NVD · CVE.org · FIRST EPSS

An information disclosure vulnerability exists in the Syslog functionality of D-LINK DIR-3040 1.13B03. A specially crafted network request can lead to the disclosure of sensitive information. An attacker can send an HTTP request to trigger this vulnerability.

Published
Jul 16, 2021
Updated
Jun 16, 2026
EPSS
32.3% · 98th percentile

Report tools

JSON

Action score

27

Monitor

Low priority for now.

CVSS
17 / 40 · 4.3 / 10
CISA KEV
0 / 30 · Not listed
EPSS
10 / 30 · 32.3%

CNA vs NVD score

NVD
4.3
CNA · talos
6.5
2.2 point gap

CVSS:3.0/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:N/A:N

The score given by the assigning authority versus NVD’s independent score. A gap means the severity is contested.

Get told when this record changes

  • Not in KEV: no record of exploitation in the wild
  • Proof of concept exists, no weaponized module
  • No fixed version yet

If any of these changes, we'll tell you in the daily email digest.

Follow CVE-2021-21816

When you'll hear from us

  • when it enters CISA KEV
  • when exploit code appears or is weaponized
  • when the record is updated (including a fixed version)
  • when EPSS rises 20 points in a week

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Noroxi analysis

What does it mean in your environment?

The assessment above is generated automatically from the record's data; it doesn't know your environment. Our team verifies on your systems whether this vulnerability is actually exploitable and which mitigation is enough.

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Affected systems

Is your version affected?

Pick the product and type the version you run. It's compared with this record's version ranges in your browser; the version isn't sent anywhere.

VendorProduct
dlinkdir-3040 firmware
dlinkdir-3040

Versions reported by the vendor

Affected version ranges reported by the assigning authority (talos). Independent of NVD's CPE analysis and usually ahead of it.

  • n/a D-LINK

    • D-LINK DIR-3040 1.13B03affected

Affected versions

NVD version ranges (for catalog products). Add the product to your stack with a version and matching uses these.

  • dlink dir-3040 firmware1.13b03

Same product

dlink: all records

Other highest-scoring records for the same primary product.

  • CVE-2022-44832D-Link DIR-3040 device with firmware 120B03 was discovered to contain a command injection vulnerability via the SetTriggerLEDBlink function.
    40Plan
  • CVE-2021-21913An information disclosure vulnerability exists in the WiFi Smart Mesh functionality of D-LINK DIR-3040 1.13B03.
    40Plan
  • CVE-2021-21820A hard-coded password vulnerability exists in the Libcli Test Environment functionality of D-LINK DIR-3040 1.13B03.
    40Plan

Published before and after this one in the same product

  • Later →CVE-2021-21817Jul 16, 2021 · An information disclosure vulnerability exists in the Zebra IP Routing Manager functionality of D-LINK DIR-3040 1.13B03.
    31Monitor
  • Later →CVE-2021-21818Jul 16, 2021 · A hard-coded password vulnerability exists in the Zebra IP Routing Manager functionality of D-LINK DIR-3040 1.13B03.
    31Monitor
  • Later →CVE-2021-21819Jul 16, 2021 · A code execution vulnerability exists in the Libcli Test Environment functionality of D-LINK DIR-3040 1.13B03.
    29Monitor

Remediation

Which version to upgrade to

Fix versions compiled from the vendor, package registries and Microsoft. Verify the vendor's note before upgrading.

No fix version is recorded for this entry. Check the references for vendor advisories.

Exploit status

Proof of concept available

A public proof of concept or detection signature exists. Exploit knowledge is out there; don't delay patching.

Evidence

  • Nuclei detection template ×1

Noroxi does not host or link to exploit code. Metasploit module names and Nuclei template ids are shown (names, not code); Exploit-DB entries and PoC repositories are given as counts only.

Public exploit evidence
SourceKindDate
Nuclei detection templateNuclei template CVE-2021-21816 —

Research context

For pentesters and researchers: attack profile, score disagreement, timeline, patch commits, credits, variant and chain candidates, bug bounty scope. All derived from existing data; no exploit code.

Timeline

From publication to today: proof of concept, Metasploit module, CISA KEV and fix record. Dates are as reported by the sources.

No dated events beyond publication.

EPSS, last 120 days

FIRST EPSS daily score; only changes of 0.01 or more are recorded (step chart).

Not on record for this CVE: patch commit or PR link · researcher credit · variant or chain candidate · public bounty program.

Technical details

Attack conditions

  • Anyone who can reach it over the internet can trigger it.
  • No account or password is required.
  • A user must open a link or visit a page.
  • No special conditions are required; it is repeatable.

If successful

Confidentiality
low · data can be read
Integrity
none
Availability
none
Attack vector
Network
Attack complexity
Low
Privileges required
None
User interaction
Required
Scope
Unchanged
Confidentiality impact
Low
Integrity impact
None
Availability impact
None

Weakness class (CWE)

CWE-200 · Exposure of Sensitive Information to an Unauthorized Actor

CVSS vector

CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:L/I:N/A:N

nvd-primary

Root cause

The extension requests broader permissions than its function needs and sends the data it collects out for purposes beyond its stated function.

The bug in code

The whole CWE-200 class

A representative example of this vulnerability class. Not the vendor's source code; it shows the faulty pattern and its fix.

Vulnerable

json
{  "permissions": ["tabs", "<all_urls>"],  "background": { "service_worker": "analytics.js" }}

Fixed

json
{  "permissions": ["activeTab"],  "host_permissions": ["https://yildiz.example/*"]}

Attack context

MITRE CAPEC attack patterns and ATT&CK techniques for this weakness class (CWE). A starting point for detection rules and threat hunting.

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