CVE-2021-40655
An informtion disclosure issue exists in D-LINK-DIR-605 B2 Firmware Version : 2.01MT. An attacker can obtain a user name and password by forging a post request to the / getcfg.php page
- CVSS
- 7.5Highscored by CISA
- Exploited in the wild
- Yes, in CISA KEV since 16 May 2024CISA deadline for US federal agencies: 6 Jun 2024
- EPSS
- 87.0%chance of exploitation in the next 30 daystop 0.3% of scored CVEsFIRST score of 11 Nov 2026
- Fix
- Patch availablesee the advisories in the references
- Published
- 24 Sept 2021analysed here 12 Nov 2026
Do first. 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. (CISA's required action for this KEV entry)
Summary
Triage
- Attack surface
- Server-side
- Exploitable
- At runtime
- Attack vector
- network
- Weakness
- CWE-863 Incorrect Authorization
The summary, impact and action text on this page are written by our AI analysis pipeline, or taken from the NVD description when a CVE was imported from NVD. They are not the vendor's wording: check them against the sources. A longer AI executive summary and technical analysis are generated for signed-in accounts on the Max plan.
Affected products
Products named in our analysis
- dlink:dir-605l_firmware
Fix and mitigation
WAF and other mitigations
Can a WAF block it? Partly. The attacker sends a forged HTTP POST request to a specific web interface page to obtain credentials, which can be detected by monitoring unusual POST requests to that endpoint. A WAF rule can match POST requests to /getcfg.php endpoint. No tracked WAF vendor has published a rule for this CVE yet, so you would write it yourself.
What a custom rule would match: POST requests to /getcfg.php endpoint
Also consider: patch · custom WAF rule · per-resource ACL
Based on an AI reading of the CVE description, and no vendor rule found yet. We check Cloudflare, AWS, Google Cloud Armor and Azure; for Akamai, Imperva, Fastly, F5, ask your vendor.
Remediation steps (AI-written)
Step-by-step remediation is generated for accounts on the Max plan, for CVEs that match a technology in their stack. Add this technology to your stack to see the fix checklist.
Exploitation evidence
- CISA KEV catalog
- Listed since 16 May 2024.
- CISA due date
- 6 Jun 2024, the remediation deadline for US federal agencies
- 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.
- Public exploit code
- Detection templates only, no public exploit found: 1 Nuclei template
- CISA SSVC
- exploitation active, automatable no, technical impact partialAssessed by CISA 4 Feb 2025 (SSVC 2.0.3). Exploitation is none, poc (public proof of concept) or active.
Nuclei
- D-Link DIR-605 - Information Disclosuredetection template, high
Listed so you can judge urgency, not as a recommendation to run anything. GitHub “proofs of concept” are unvetted: some are fake or carry malware. Exploit-DB marks the entries its staff verified.
Timeline
- 24 Sept 2021Published
- 16 May 2024Added to CISA KEV (exploited in the wild)964 days (about 3 years) later
- 6 Jun 2024CISA remediation due date (US federal agencies)21 days later
- 4 Feb 2025CISA SSVC assessment: exploitation active244 days (about 8 months) later
- 21 Oct 2025CVE record last updated259 days (about 9 months) later
- 12 Nov 2026Analysed by vulneraibility.com387 days (about 1 year) later
CVSS vector
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N
| Metric | Value | What it means |
|---|---|---|
| Attack vector | NetworkReachable over the internet or any routable network. | Reachable over the internet or any routable network. |
| Attack complexity | LowRepeatable attack, no special conditions. | Repeatable attack, no special conditions. |
| Privileges required | NoneThe attacker needs no prior access. | The attacker needs no prior access. |
| User interaction | NoneNo victim action needed. | No victim action needed. |
| Scope | UnchangedImpact stays within the vulnerable component. | Impact stays within the vulnerable component. |
| Confidentiality | HighTotal data disclosure possible. | Total data disclosure possible. |
| Integrity | NoneNo unauthorised modification. | No unauthorised modification. |
| Availability | NoneThe service stays up. | The service stays up. |
Common questions
Is CVE-2021-40655 being exploited?
Yes. CVE-2021-40655 appears in CISA's Known Exploited Vulnerabilities catalog, which means exploitation in the wild has been confirmed and reported. Treat it as active rather than theoretical, and patch it ahead of higher-scoring vulnerabilities that carry no exploitation evidence.
How severe is CVE-2021-40655?
CVE-2021-40655 is rated High with a CVSS score of 7.5. Severity describes how bad exploitation would be, not how likely it is: pair it with exploitation evidence before deciding what to patch first.
Is there a patch for CVE-2021-40655?
Yes. A fix has been recorded for CVE-2021-40655. The vendor advisory is the authority on the exact fixed version — apply it from there rather than from a summary.
What does CVE-2021-40655 affect?
CVE-2021-40655 affects dlink:dir-605l_firmware. Confirm the exact affected versions against the vendor advisory before deciding you are exposed.
Exploitation status reflects CISA's KEV catalog as we last synced it. Check the catalog directly.
References
3 references in the CVE record, grouped by the tags the record gives them.
Other links (3)
- dlink.com /en/security-bulletin/
- github.com /Ilovewomen/D-LINK-DIR-605/
- cisa.gov /known-exploited-vulnerabilities-catalog?field_cve=CVE-2021-40655
Where the data on this page comes from
- CVE List (CVE.org): description, affected versions, references; CVE Terms of Use
- NVD: CVSS and CPE data
- CISA KEV catalog: exploitation, date added, due date
- CISA Vulnrichment (ADP): SSVC decision points
- FIRST EPSS: exploit probability and percentile
- Nuclei templates: detection templates
Summary, impact and triage tags: written by our AI analysis pipeline from the sources above. Check them against the sources.
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