CVE-2020-25506
CVE-2020-25506 is a security flaw in D-Link DNS-320 Device, routers for homes and small offices. Attackers can run their own code on D-Link DNS-320 Device. The US Cybersecurity and Infrastructure Security Agency (CISA) added it to its catalog of flaws known to be used in attacks on 3 Nov 2021.[1]
D-Link DNS-320 Device 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 a command injection in D-Link DNS-320 Device. In its words: “D-Link DNS-320 device contains a command injection vulnerability in the sytem_mgr.cgi component that may allow for remote code execution.”[1]
The underlying weakness is OS command injection (CWE-78), in MITRE’s list of common software weaknesses.[2]
It scores 9.8 out of 10 on the Common Vulnerability Scoring System, which rates it critical, 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 DNS-320 Device.
Every device with D-Link DNS-320 Device needs the update.
Exploitation
CISA added it to its catalog of known exploited vulnerabilities on 3 Nov 2021, 274 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 3 May 2022 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 over 99%. That’s in the top 1% of the flaws it scores.[4]
CISA assesses it as automatable: attackers can run it against many targets at once.
CISA doesn’t say who was attacked, or how.
Fix
D-Link has published a fix or advice.[3] CISA’s required action: “Apply updates per vendor instructions.”[1]
- Update D-Link DNS-320 Device 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 9.8.[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 over 99%.[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 OS command injection flaws
- CVE-2026-110447, Collabora Online – Built-in CODE Server: online – built-in CODE server OS command injection ·
- CVE-2026-106931, EG Secure Solutions SiteGuard Server Edition: OS command injection ·
- CVE-2026-83549, SonicWall SMA1000 Appliances: OS command injection ·
- CVE-2026-49869, Kestra OSS: OSS OS command injection ·
- CVE-2026-73570, Synacor Zimbra Collaboration Suite (ZCS): OS command injection ·
Added the same day
- CVE-2021-42258, BQE BillQuick Web Suite: SQL injection ·
- CVE-2021-42013, Apache HTTP Server: path traversal ·
- CVE-2021-41773, Apache HTTP Server: path traversal ·
- CVE-2021-40539, Zoho ManageEngine: aDSelfService plus authentication bypass ·
- CVE-2021-40444, Microsoft MSHTML: remote code execution ·
Every D-Link flaw on CISA’s list · Everything added in November 2021
References
- ^ Cybersecurity and Infrastructure Security Agency. “D-Link DNS-320 Device Command Injection Vulnerability”. Known Exploited Vulnerabilities Catalog, added 3 Nov 2021.
- ^ National Institute of Standards and Technology. “CVE-2020-25506 Detail”. National Vulnerability Database, published 2 Feb 2021.
- ^ D-Link. Advisories and fixes: supportannouncement.us.dlink.com, dlink.com.
- ^ FIRST. “Exploit Prediction Scoring System”. EPSS 1.000, percentile 100.0, 31 Oct 2026.
- CVE Program. “CVE-2020-25506”. 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.