Sunday, November 20, 2011

Vulnerable Weekends #1

Last week Mozilla revised the major version number for its popular web browsing application, Firefox, taking it to version 8.0. Its been hardly a few days since Firefox 8.0 has been available publicly, reports about a denial of service (DoS) vulnerability within the latest and prior releases started to make news. I have tried to analyze this vulnerability and #1A is a report for the same.

The #1B report provides yet another interesting update related to a remote code execution (RCE) vulnerability confirmed within ProFTPd.

Vulnerability Report #1A: Mozilla Firefox OnStartRequest() Function XPCOM Object Processing Denial of Service Vulnerability

Vulnerable Product: Installations of Mozilla Firefox with versions 8.0 and prior.

CVE ID: Not available

Access Vector: NETWORK
Access Complexity: MEDIUM
Authentication: NONE

Confidentiality Impact: NONE
Integrity Impact: NONE
Availability Impact: PARTIAL
Base Score: 4.3

Exploitability: PROOF-OF-CONCEPT
Remediation Level: UNAVAILABLE
Report Confidence: UNCORROBORATED
Temporal Score: 3.7

Mozilla Firefox, the popular open source web browsing application, reportedly contains a vulnerability which could be leveraged by an attacker to cause a denial of service (DoS) condition on the targeted system.

The vulnerable web browser performs insufficient sanitization on user-supplied input encountered while processing crafted webpages.

Online reports indicate that the OnStartRequest() function which is defined within the nsObjectLoadingContent.cpp source file of the affected software is where the vulnerability resides. This function erroneously permits a comparison between a Cross Platform Common Object Model (XPCOM) object with a NULL value received as input. This flaw could return a NS_BINDING_ABORTED value to the calling function, leading to an abnormal termination of the vulnerable web browser.

An attacker who can successfully lure a targeted user to visit a malicious webpage that contains crafted input for the vulnerable function or who can persuade a user to open a malicious web page received as an e-mail attachment, could trigger this vulnerability. When the vulnerable web browser tries to process such crafted webpages, the above mentioned flaw is triggered, leading to the DoS condition on the targeted system.

Proof-of-concept (PoC) code to demonstrate the validity of the vulnerability claim and an impact of a successful exploit attempt has been made available on public sources like Exploit-DB.

The vendor, Mozilla, has not yet confirmed this vulnerability and as such there are no official patches or updates available for this vulnerability. Users are requested to get in touch with the vendor's support services to obtain updates for their installations.

Vulnerability Sources:

Vulnerability Report #1B: ProFTPd pr_cmd_dispatch_phase() Function Response Code Handling Arbitrary Code Execution Vulnerability

Vulnerable Product:
Installations of ProFTPd versions with 1.3.3 and prior.

CVE ID: CVE-2011-4130

Access Vector: NETWORK
Access Complexity: LOW
Authentication: SINGLE

Confidentiality Impact: COMPLETE
Integrity Impact: COMPLETE
Availability Impact: COMPLETE
Base Score: 9.0

Exploitability: UNPROVEN
Remediation Level: OFFICIAL FIX
Report Confidence: CONFIRMED
Temporal Score: 6.7

ProFTPd, the popular FTP daemon, reportedly contains a vulnerability which could be leveraged by an attacker to execute arbitrary code on the targeted system.

The vulnerable daemon fails to manage a pool used for the client responses. While processing user requests, if an exceptional condition occurs, the daemon uses a response pointer to select user response to be sent for the triggered exception. However, due to a flaw within the code responsible for handling exceptions, the response pointer is incorrectly restored to the appropriate response code and it could be made to point to a desired memory location.

Online reports indicate that the pr_cmd_dispatch_phase() function defined within the main.c source file of the vulnerable daemon is where the vulnerability resides. The vulnerable function provides a mechanism for issuing calls to the registered ProFTPd modules. However, before entering the requested module, the daemon essentially stores the resp_pool state so that it can be used upon return. While the control is within the requested module, if an exception is triggered, the vulnerable daemon fails to restore resp_pool state, which could then be altered using a controlled memory corruption.

An attacker who can complete the initial authentication phase on the targeted system could successfully trigger this vulnerability. When the vulnerable daemon tries to handle an explicitly triggered exception, it could allow arbitrary code execution on the targeted system.

The vendor,, has confirmed this vulnerability and provided official updates to mitigate it. Users are requested to immediately apply the latest updates on their vulnerable installations.

Vulnerability Sources:

Generic Sources:

Wednesday, November 16, 2011

Vulnerable Weekends - Introduction

Starting this week onwards, I will be posting regular updates related to the latest vulnerability reports submitted in the wild. Using this blog, I will try to analyse and post updates for around 1 to 2 vulnerability reports each weekend, prioritizing on the ones that involve highest security risks.

Vulnerability analysis and reporting includes multiple facets, most of which are very well documented online. As such, I mostly aim to cover the extremely important information in the vulnerability reports published here. I will include necessary references wherever applicable.

Readers are kindly requested to leave behind their comments. Whether you like/dislike the analysis, want me to make any changes in the report format or require additional details, just let your concerns known via the comments section or reach out via mails.

Have a secure weekend!