D-Link DSL-320B-D1 Pre-Authentication Buffer Overflow

2021.04.08
Risk: High
Local: No
Remote: Yes
CWE: CWE-119

-----BEGIN PGP SIGNED MESSAGE----- Hash: SHA512 Multiple Pre-Auth Stack Buffer Overflow in D-Link DSL-320B-D1 ADSL Modem ======== < Table of Contents > ========================================= 0. Overview 1. Details 2. Solution 3. Disclosure Timeline 4. Thanks & Acknowledgements 5. References 6. Credits 7. Legal Notices ======== < 0. Overview > =============================================== Release Date: 7 March 2021 Revision: 1.0 Impact: The ADSL modem DSL-320B-D1, version EU_1.25 and lower, is affected to multiple Stack Buffer Overflows that allow unauthenticated remote attackers to takeover the device. Severity: Critical CVSS Score: 9.8 (CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H) CVE-ID: CVE-2021-26709 Vendor: D-Link Affected Products: DSL-320B-D1 Affected Versions: EU_1.25 and lower ======== < 1. Details > ================================================ During a Penetration Test it was possible to identify and exploit multiple Stack Buffer Overflows (1) in the D-Link DSL-320B-D1 ADSL modem ,a now legacy model, which is distributed in the past by Telecom Italia on loan for use together with the residential ADSL line. The vulnerabilities are present in the login functionality, exposed by "login.xgi" with "user" and "pass" parameters. [[ GET /login.xgi?user=" + payload + "&pass=abcde HTTP/1.1\nHost: " + host + "\n\n" ]] To exploit the vulnerability using "user" parameter, you need construct the payload like the following: [[ OFFSET = 652 ADDR = 0x7ffe8ab0 payload = "A"*OFFSET payload += pack(">I", ADDR) payload += shellcode ]] While the "pass" parameter uses 641 as offset. The payload must be passed as parameter value in a GET request. You can found a working shellcode here: https://www.exploit-db.com/shellcodes/45541 You will have to change the ip/port to match your network configuration. Using ROP is possible to avoid to use the hardcoded addresses. ======== < 2. Solution > =============================================== Refer to D-Link Support Announcements "SAP10216" for details (2). ======== < 3. Disclosure Timeline > ==================================== 09/01/2021 : Discovery of the vulnerability 23/01/2021 : Vulnerability submitted to vendor 25/01/2021 : Vendor request more info about exploit the vulnerabilities 27/01/2021 : Sent details to vendor 01/02/2021 : Request status update to the vendor 13/02/2021 : Sent CVE assigned by mitre to vendor 13/02/2021 : Vendor response, analysis in progress 30/03/2021 : Request status update to the vendor 30/03/2021 : Vendor confirm the vulnerabilities 07/04/2021 : Public disclosure ======== < 4. Thanks & Acknowledgements > ============================== D-Link US SIRT ======== < 5. References > ============================================= (1) https://cwe.mitre.org/data/definitions/121.html (2) https://supportannouncement.us.dlink.com/announcement/publication.as px?name=SAP10216 (3) https://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2021-26709 ======== < 6. Credits > ================================================ This vulnerability was discovered and reported by: Gabriele 'matrix' Gristina (gabriele DOT gristina AT gmail DOT com) Contacts: https://www.linkedin.com/in/gabrielegristina https://twitter.com/gm4tr1x https://github.com/matrix/ ======== < 7. Legal Notices > ========================================== Copyright (c) 2021 Gabriele 'matrix' Gristina Permission is granted for the redistribution of this alert electronically. It may not be edited in any way without mine express written consent. If you wish to reprint the whole or any part of this alert in any other medium other than electronically, please email me for permission. Disclaimer: The information in the advisory is believed to be accurate at the time of publishing based on currently available information. Use of the information constitutes acceptance for use in an AS IS condition. There are no warranties with regard to this information. Neither the author nor the publisher accepts any liability for any direct, indirect, or consequential loss or damage arising from use of, or reliance on,this information. -----BEGIN PGP SIGNATURE----- iQIzBAEBCgAdFiEElKssfhju0ogMPPCn7SvzgGQpUxsFAmBuug8ACgkQ7SvzgGQp UxsERA//SsjAPq95yZItWPBiSrOSxUuRUUAzwzuo4bIYNb5bjfMDgB/HsnwwtG5W yPXUoKWHLxyaX3nconGirDOHNSYNTd23sYXx+K3T97l/cPNZ3Nv5vk9DRDK76NNc Xe2v7WdBBS1jAbuKKAHv8ioc+uxPs9oi9Iz70Uv9pQsaq2QSm6B+AX5s0fQIsgje glPPYMLAasdmr4Wwk6XBOrzw8zvnkMxaRGsIJ2QmIpl7kmiN2BivSSKWfS8rUhEG RfhIyTjDyN1yHU+GOTEJe04D8CjpLSUCsfFz7BxPYs1IFK44RZfiMJp4c7o7vMPG uXJWpeq6wfraCh/g/JY5rvOpiyYC5e+mtg8MQjJW5ZEkK8Szg14douVn/bLsRFIc cEs3mImqE/8pwksKDRLqAUq9/Q1dt5FRwFLJDpX5e18bwR1XOU1+iRMQJuUGBnre UEibw1u8bSjJakFi9gCXQC2LrvbAC/tc97I42bA7qhiJxmOaMdPWt/C7Is/bVdYB JdVUej2eMBlsmfVaPbM6aT18+Z9sfIMKaGq9nAbBmY+DNI6gBfX0ty8X1o39ADcQ I+DEXnKBZP1YhWlvYYR5mBMYs9wJzw8OGyeGqK2LU1tmWfF9d0drXK5pvK1sSpQh /ytQ4g/jSRp+UBK7Ulxep08gCphGuAkc7NuKsbHh4YgkCbIaIDI= =4j+1 -----END PGP SIGNATURE-----


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