Zero-day vulnerability in Dir-100

Security bypass
CVE-2013-6026

Vulnerability details

Advisory: SB2013101201 - Backdoor in D-Link routers

Vulnerable component: Dir-100

CVE-ID: CVE-2013-6026

CVSSv3 score: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H/E:F/RL:O/RC:C

CWE-ID: CWE-113 - Improper Neutralization of CRLF Sequences in HTTP Headers ('HTTP Response Splitting')

Description:

The vulnerability allows a remote attacker to bypass security restrictions on the target system.

The weakness exists due to an error in the alpha_auth_check() function. By setting the user agent string to xmlset_roodkcableoj28840ybtide, an attacker can send an HTTP request to bypass authentication and obtain administrative access to the device.

Successful exploitation of the vulnerability results in full access to the vulnerable system.

Note: the vulnerability was being actively exploited.

External links:

http://www.devttys0.com/2013/10/reverse-engineering-a-d-link-backdoor/
https://packetstormsecurity.com/files/123848/D-Link-Backdoor-Czechr.html
http://www.securityspace.com/smysecure/catid.html?id=1.3.6.1.4.1.25623.1.0.103810
https://www.symantec.com/security_response/attacksignatures/detail.jsp?asid=27130
https://krebsonsecurity.com/2013/12/important-security-update-for-d-link-routers/

About zero-day vulnerabilities

Zero-day vulnerability is an undisclosed vulnerability in software that hackers can exploit to compromise computer programs, gain unauthorized access to sensitive data, penetrate networks, etc. We consider vulnerability a zero-day when there is no solution provided from software vendor and the vulnerability is being actively exploited by malicious actors.

Zero-day candidate is a potential zero-day vulnerability in software which might have been used in targeted attacks, however there is no evidence to support this suggestion.