Netgear WNR2000v3/WNR2000v4/WNR2000v5 uhttpd /apply.cgi stack-based overflow

Summaryinfo

A vulnerability identified as critical has been detected in Netgear WNR2000v3, WNR2000v4 and WNR2000v5. This affects an unknown part of the file /apply.cgi of the component uhttpd. Performing a manipulation results in stack-based overflow. Remote exploitation of the attack is possible. Furthermore, an exploit is available.

Detailsinfo

A vulnerability classified as critical has been found in Netgear WNR2000v3, WNR2000v4 and WNR2000v5 (Wireless LAN Software) (affected version not known). This affects some unknown functionality of the file /apply.cgi of the component uhttpd. The manipulation with an unknown input leads to a stack-based overflow vulnerability. CWE is classifying the issue as CWE-121. A stack-based buffer overflow condition is a condition where the buffer being overwritten is allocated on the stack (i.e., is a local variable or, rarely, a parameter to a function). This is going to have an impact on confidentiality, integrity, and availability.

The weakness was published 12/20/2016 by Pedro Ribeiro as [0-day] RCE and admin credential disclosure in NETGEAR WNR2000 as not defined mailinglist post (Full-Disclosure). It is possible to read the advisory at seclists.org. The exploitability is told to be easy. It is possible to initiate the attack remotely. No form of authentication is needed for exploitation. Technical details and a public exploit are known.

A public exploit has been developed by Pedro Ribeiro in HTTP POST Request and been published immediately after the advisory. The exploit is shared for download at seclists.org. It is declared as proof-of-concept. The vulnerability was handled as a non-public zero-day exploit for at least 85 days. During that time the estimated underground price was around $5k-$25k. The code used by the exploit is:

POST /apply.cgi?/lang_check.html%20timestamp=14948715 HTTP/1.1
Authorization: Basic YWRtaW46cGFzc3dvcmQ=
Content-Type: application/x-www-form-urlencoded
Content-Length: 604

submit_flag=select_language&hidden_lang_avi=aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaAAAABBBBCCCCDDDDEEEEFFFFbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbb

As it can be seen above, a stack variable which is located at an offset of 0x38 is the one overflown and it is in this function that the crash shown in gdb above occurs. The first register we control, $s0, has its value stored at offset 0x14, which is stored in the stack 0x24 (36) bytes from the stack variable that gets overwritten.

The mailinglist post contains the following remark:

NETGEAR did not respond to any emails, so THERE IS NO FIX for this vulnerability. It is recommended to replace this router with another make and model that supports OpenWRT firmware.

Similar entries are available at VDB-94633 and VDB-94634. Statistical analysis made it clear that VulDB provides the best quality for vulnerability data.

Productinfo

Type

• Wireless LAN Software

Vendor

• Netgear

Name

• WNR2000v3
• WNR2000v4
• WNR2000v5

License

• commercial

Website

• Vendor: https://www.netgear.com/

CPE 2.3info

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CPE 2.2info

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Entryinfo

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