CVE-2021-40655
CVE-2021-40655 is a security flaw in D-Link DIR-605 Router, routers for homes and small offices. Attackers can read information from D-Link DIR-605 Router that should be private. The US Cybersecurity and Infrastructure Security Agency (CISA) added it to its catalog of flaws known to be used in attacks on 16 May 2024.[1]
D-Link DIR-605 Router is in things households have: home and small-office routers, so the fix matters at home as much as at work. D-Link has published a fix or advice.
Description
CISA calls it an information disclosure in D-Link DIR-605 Router. In its words: “D-Link DIR-605 routers contain an information disclosure vulnerability that allows attackers to obtain a username and password by forging a post request to the /getcfg.php page.”[1]
The underlying weakness is incorrect authorization (CWE-863), in MITRE’s list of common software weaknesses.[2]
It scores 7.5 out of 10 on the Common Vulnerability Scoring System, which rates it high, scored by NVD using CVSS 3.1.[2]
Affected versions
NVD’s record doesn’t list version ranges for it; D-Link’s advisory has them[3]. CISA names the product as D-Link DIR-605 Router.
Every device with D-Link DIR-605 Router needs the update.
Exploitation
CISA added it to its catalog of known exploited vulnerabilities on 16 May 2024, 965 days after it was made public. CISA lists a flaw only when it has reliable evidence of it being exploited, and gave US federal agencies until 6 Jun 2024 to fix it.[1]
FIRST’s Exploit Prediction Scoring System, which estimates how likely a flaw is to be used in attacks in the next 30 days from what it sees across the internet, puts it at 87%. That’s in the top 1% of the flaws it scores.[4]
CISA assesses it as not automatable: each attack takes some work.
CISA doesn’t say who was attacked, or how.
Fix
D-Link has published a fix or advice.[3] CISA’s required action: “This vulnerability affects legacy D-Link products.”[1]
- Update D-Link DIR-605 Router now.Open the router’s app, or its admin page in a browser, and look for a firmware update. Then turn on automatic updates, so the next fix arrives on its own.
- If the maker has stopped updating it, replace it.Routers stop getting fixes after a few years, and attackers keep a list of the ones that did. If there’s no newer firmware, it won’t be fixed.
Timeline
| Date | Event |
|---|---|
| The flaw is made public in the National Vulnerability Database, with a severity score of 7.5.[2] | |
| CISA adds it to its catalog of flaws known to be used in attacks.[1] | |
| CISA’s deadline for US government agencies to fix it.[1] | |
| FIRST puts the odds of it being used in attacks in the next 30 days at 87%.[4] |
See also
Other D-Link flaws
- CVE-2025-29635, D-Link DIR-823X: command injection ·
- CVE-2022-37055, D-Link Routers: buffer overflow ·
- CVE-2022-40799, D-Link DNR-322L: download of code without integrity check ·
- CVE-2020-25079, D-Link DCS-2530L and DCS-2670L Devices: DCS-2530L and DCS-2670L command injection ·
- CVE-2020-25078, D-Link DCS-2530L and DCS-2670L Devices: unspecified ·
Other incorrect authorization flaws
- CVE-2026-71362, Adobe Commerce and Magento: incorrect authorization ·
- CVE-2026-42016, JFrog Artifactory: incorrect authorization ·
- CVE-2025-54253, Adobe Experience Manager (AEM) Forms: experience manager forms code execution ·
- CVE-2025-55177, Meta Platforms WhatsApp: incorrect authorization ·
- CVE-2025-21480, Qualcomm Multiple Chipsets: incorrect authorization ·
Added the same day
- CVE-2024-4761, Chrome and other Chromium browsers: out-of-bounds memory write ·
- CVE-2014-100005, D-Link DIR-600 Router: cross-site request forgery (CSRF) ·
Every D-Link flaw on CISA’s list · Everything added in May 2024
References
- ^ Cybersecurity and Infrastructure Security Agency. “D-Link DIR-605 Router Information Disclosure Vulnerability”. Known Exploited Vulnerabilities Catalog, added 16 May 2024.
- ^ National Institute of Standards and Technology. “CVE-2021-40655 Detail”. National Vulnerability Database, published 24 Sep 2021.
- ^ D-Link. Advisories and fixes: legacy.us.dlink.com, dlink.com.
- ^ FIRST. “Exploit Prediction Scoring System”. EPSS 0.870, percentile 99.7, 31 Oct 2026.
- CVE Program. “CVE-2021-40655”. The official CVE record.
This article is built from CISA’s catalog (version 2026.10.30), NVD’s record and FIRST’s scores, kept in HARD’s database and checked every morning. The plain English is HARD’s.