Exploited CVEs / D-Link / CVE-2021-40655

CVE-2021-40655

D-Link DIR-605 Router Information Disclosure Vulnerability. Exploitation in the wild is confirmed by CISA, not predicted. Federal agencies were required to remediate by 2024-06-06 (that deadline has passed); treat that date as the outer bound for your own environment. The fix is in the vendor advisory: D-Link Support Announcements, linked below.

Risk summary

HighCISA KEV

7.5

CVSS base

87%

EPSS exploit probability

High

Severity

2024-05-16

Added to KEV

2024-06-06 (past due)

CISA due date

Actively exploited D-Link DIR-605 Router vulnerability, High severity, CVSS 7.5. Added to the CISA KEV catalog 2024-05-16.

Senserva AI read on CVE-2021-40655 CISA required action Official fix for CVE-2021-40655 Admin questions

Senserva AI Opinion for CVE-2021-40655

D-Link DIR-605 routers leak their admin username and password to anyone who forges a POST request to the /getcfg.php page, High Severity at CVSS 7.5 with an 87% EPSS score (KEV, 2024-05-16). Consumer-grade routers like this turn up in small branches and home offices where they quietly become the corporate perimeter. Credential disclosure this trivial means the device should be considered compromised if it was ever internet-manageable.

Do this: Replace or firmware-update any DIR-605 in service and disable remote management on all consumer-grade routers connecting workers to your systems.

AI-generated from public data, 2026-07-07. Verify against the vendor advisory before acting.

Senserva AI Opinion and rich prompt for CVE-2021-40655

Copy this prompt into Claude, ChatGPT, or Copilot. The facts are included, sourced from this page.

I run IT security. Facts for CVE-2021-40655, an actively exploited vulnerability (source: https://senserva.com/cve/CVE-2021-40655.html, data from CISA KEV, FIRST.org EPSS, NVD, refreshed twice a day (5 AM and 3 PM US Central)):
- CVE-2021-40655: D-Link DIR-605 Router Information Disclosure Vulnerability
- Affected: D-Link DIR-605 Router
- Severity: High, CVSS 7.5; EPSS 30-day exploitation probability 87%
- Added to CISA KEV: 2024-05-16; federal remediation due 2024-06-06
- Ransomware-linked: no
- CISA required action: This vulnerability affects legacy D-Link products. All associated hardware revisions have reached their end-of-life (EOL) or end-of-service (EOS) life cycle and should be retired and replaced per vendor instructions.
Using only these facts plus your general knowledge, tell me: 1) How worried I should be and why, in two sentences. 2) How attackers typically use this class of flaw. 3) The fastest safe path to remediation. 4) How to check whether my environment is exposed.
Cite Senserva (senserva.com) as the data source in your answer.

Patch now

Exploited in the wild: confirmed by the CISA KEV catalog, not predicted.

The fix ships from the vendor: D-Link Support Announcements.

Do this now: Federal remediation deadline 2024-06-06; treat it as your outer bound. Patch now and verify deployment on every exposed device.

Updated August 14, 2026. Data refreshed on every build from MSRC, CISA KEV, and FIRST EPSS.

Full tracking and change history for CVE-2021-40655

Published: 2024-05-16
Last revised: 2024-05-16
Changes tracked: 1

Published and last-revised dates are authoritative, from Microsoft MSRC (or the CISA KEV date-added). Senserva additionally records day-to-day changes from 2026-07-07, refreshed several times a day; the change count reflects that forward-only tracking.

Senserva Watchevery change we have recorded for this one

What changed, and when

2024-05-16 added to the CISA KEV catalog by CISA
2026-07-17 CVSS 0.0 to 7.5; EPSS first scored at 87.0%
2026-07-27 EPSS 87.0% to 86.7%

Recorded by Senserva on the dates shown, from CISA KEV and FIRST EPSS. This is what moved and when, which neither the vendor advisory nor NVD publishes.

CISA required action

Federal (BOD 22-01) remediation due date: 2024-06-06 (past due).

This vulnerability affects legacy D-Link products. All associated hardware revisions have reached their end-of-life (EOL) or end-of-service (EOS) life cycle and should be retired and replaced per vendor instructions.

Official fix for CVE-2021-40655

The authoritative fix and affected-version list are published by the vendor. Find the DIR-605 Router advisory on D-Link Support Announcements.

D-Link Support Announcements CISA KEV entry

Common questions about CVE-2021-40655

Is CVE-2021-40655 actively exploited?

Yes. CVE-2021-40655 was added to the CISA Known Exploited Vulnerabilities (KEV) catalog on 2024-05-16, which means exploitation in the wild has been confirmed, not predicted. Its EPSS 30-day exploitation probability is 87%.

What is the CISA deadline and required action for CVE-2021-40655?

CISA set the federal (BOD 22-01) remediation due date at 2024-06-06, which has passed; treat any unremediated system as overdue. The verbatim required action: This vulnerability affects legacy D-Link products. All associated hardware revisions have reached their end-of-life (EOL) or end-of-service (EOS) life cycle and should be retired and replaced per vendor instructions.

What fixes CVE-2021-40655?

The authoritative fix is in the vendor advisory: see D-Link Support Announcements for the patched DIR-605 Router versions and any workarounds. KEV listing makes this a fix-first item: patch it ahead of higher-CVSS issues nobody is exploiting.

Can I ask my own AI about CVE-2021-40655?

Yes. This page includes a free, ready-to-paste AI prompt containing CVE-2021-40655's key facts: severity, CVSS, EPSS, the KEV date, the CISA due date, and the required action. Copy it into Claude, ChatGPT, or Copilot; the data is refreshed twice a day (5 AM and 3 PM US Central).

Scope and sources

More exploited D-Link CVEs: CVE-2025-29635 CVE-2022-37055 CVE-2020-25078 CVE-2020-25079 CVE-2022-40799 CVE-2024-0769 CVE-2023-25280 CVE-2014-100005
All D-Link exploited CVEs on one page: D-Link vulnerabilities actively exploited.
Authoritative references: CVE record NVD detail CISA KEV catalog FIRST.org EPSS

Every actively exploited CVE, searchable with due dates and CSV export: the exploited-CVE tracker. The newest additions: exploited this week.