CVE-2021-20165
Description
Trendnet AC2600 TEW-827DRU version 2.08B01 does not properly implement csrf protections. Most pages lack proper usage of CSRF protections or mitigations. Additionally, pages that do make use of CSRF tokens are trivially bypassable as the server does not appear to validate them properly (i.e. re-using an old token or finding the token thru some other method is possible).
AI Insight
LLM-synthesized narrative grounded in this CVE's description and references.
Trendnet AC2600 TEW-827DRU firmware 2.08B01 fails to implement proper CSRF protections, allowing attackers to perform unauthorized actions on behalf of authenticated users.
Vulnerability
The Trendnet AC2600 TEW-827DRU router running firmware version 2.08B01 lacks proper Cross-Site Request Forgery (CSRF) protections on most pages. Pages that do implement CSRF tokens do not validate them correctly, allowing reuse of old tokens or token discovery [1].
Exploitation
An attacker can craft a malicious web page or email that, when visited by an authenticated user, triggers unauthorized requests to the router's management interface. Since CSRF tokens are either absent or not properly validated, the attacker can perform actions such as changing settings or extracting sensitive information without user interaction beyond visiting the malicious page.
Impact
Successful exploitation allows an attacker to perform arbitrary actions on the router with the privileges of the authenticated user, potentially leading to full compromise of the device and network.
Mitigation
As of the publication date (2021-12-30), no firmware update has been released to address this issue. Users should restrict access to the router's management interface to trusted networks and avoid browsing untrusted sites while logged into the router.
AI Insight generated on May 27, 2026. Synthesized from this CVE's description and the cited reference URLs; citations are validated against the source bundle.
Affected products
2- Trendnet/AC2600 TEW-827DRUdescription
- Range: = 2.08B01
Patches
0No patches discovered yet.
Vulnerability mechanics
Root cause
"Missing server-side validation of CSRF tokens allows attackers to forge cross-origin requests on behalf of an authenticated administrator."
Attack vector
An attacker crafts a malicious HTML page that submits a cross-origin POST request to the router's management interface (e.g., `http://192.168.10.1/apply.cgi`). Because the server does not validate CSRF tokens properly—old or bogus tokens are accepted—the attacker can perform state-changing actions on behalf of an authenticated administrator. The services are also accessible via the WAN interface over IPv6 by default [ref_id=1], widening the attack surface. The only precondition is that the victim has an active session with the router and visits the attacker's page.
Affected code
The advisory [ref_id=1] states that "most pages lack proper usage of CSRF protections or mitigations" on the Trendnet AC2600 TEW-827DRU (version 2.08B01). Pages that do include CSRF tokens do not validate them server-side, allowing reuse of old or bogus tokens. The proof-of-concept targets the `/apply.cgi` endpoint to modify FTP user credentials.
What the fix does
The advisory [ref_id=1] does not provide a patch or specific remediation code. The recommended fix is to implement proper CSRF protections on all state-changing pages: generate a unique, unpredictable token per session, embed it in forms, and strictly validate it server-side before processing any request. Additionally, the token should be tied to the user's session and have a short expiration to prevent reuse.
Preconditions
- authThe victim must have an active authenticated session with the router's web management interface.
- inputThe attacker must trick the victim into visiting a malicious HTML page while the session is active.
- networkThe router's management interface must be reachable from the attacker's network (LAN or WAN via IPv6).
Reproduction
The advisory [ref_id=1] provides a proof-of-concept HTML page that changes an FTP user's password. Host the PoC HTML file, have an authenticated administrator visit it, and the form auto-submits a POST to `/apply.cgi` with parameters including `action=proftp` and the new password `sapphire123`. The server accepts the request because it does not validate the CSRF token.
Generated on May 25, 2026. Inputs: CWE entries + fix-commit diffs from this CVE's patches. Citations validated against bundle.
References
1- www.tenable.com/security/research/tra-2021-54mitrex_refsource_MISC
News mentions
0No linked articles in our index yet.