Insecure Handling of URL Schemes in iOS

Published: 2010-11-09
Last Updated: 2010-11-09 20:11:12 UTC
by Johannes Ullrich (Version: 1)
3 comment(s)

Nitesh Dhanjani posted a nice blog post as part of the SANS Application Security blog [1]. He discusses a particular interesting vulnerability in iOS. In iOS, like in other operating systems, application may register themselves to handle particular URL schemes. For example, a URL starting with "tel:" links to the telephone application.

However, how these URL schemes are dealt with depends on the application receiving these requests from the browser. The telephone application will for example prompt the user asking if it should dial the number. Skype on the other hand does not prompt the user. In order to prompt the user, the application has to fully load and start up. So at the very least the attacker may be able to load the application.

Desktop browsers, like for example Firefox, will first prompt the user for these external URL schemes (try "telnet:", which will launches a terminal and open telnet in most cases).


Johannes B. Ullrich, Ph.D.
SANS Technology Institute

3 comment(s)

November 2010 Microsoft Black Tuesday Summary

Published: 2010-11-09
Last Updated: 2010-11-09 18:47:36 UTC
by Johannes Ullrich (Version: 1)
7 comment(s)

Overview of the November 2010 Microsoft Patches and their status.

# Affected Contra Indications Known Exploits Microsoft rating ISC rating(*)
clients servers
MS10-087 Vulnerabiliites in Microsoft Office code execution (Replaces MS10-003 MS10-036)
Microsoft Office
KB 2423930 exploit available. Severity:Critical
Exploitability: 1
Critical Important
MS10-088 Vulnerabilities in Microsoft PowerPoint code execution (Replaces MS10-004, MS10-036, MS09-017)
Microsoft Office
KB 2293386 . Severity:Important
Exploitability: 1
Critical Important
MS10-089 Vulnerabilities in Forefront Unified Access Gateway escalation of privilege
Forefront UAG
KB 2316074 . Severity:Important
Exploitability: 1
N/A Important
We will update issues on this page for about a week or so as they evolve.
We appreciate updates
US based customers can call Microsoft for free patch related support on 1-866-PCSAFETY
(*): ISC rating
  • We use 4 levels:
    • PATCH NOW: Typically used where we see immediate danger of exploitation. Typical environments will want to deploy these patches ASAP. Workarounds are typically not accepted by users or are not possible. This rating is often used when typical deployments make it vulnerable and exploits are being used or easy to obtain or make.
    • Critical: Anything that needs little to become "interesting" for the dark side. Best approach is to test and deploy ASAP. Workarounds can give more time to test.
    • Important: Things where more testing and other measures can help.
    • Less Urgent: Typically we expect the impact if left unpatched to be not that big a deal in the short term. Do not forget them however.
  • The difference between the client and server rating is based on how you use the affected machine. We take into account the typical client and server deployment in the usage of the machine and the common measures people typically have in place already. Measures we presume are simple best practices for servers such as not using outlook, MSIE, word etc. to do traditional office or leisure work.
  • The rating is not a risk analysis as such. It is a rating of importance of the vulnerability and the perceived or even predicted threat for affected systems. The rating does not account for the number of affected systems there are. It is for an affected system in a typical worst-case role.
  • Only the organization itself is in a position to do a full risk analysis involving the presence (or lack of) affected systems, the actually implemented measures, the impact on their operation and the value of the assets involved.
  • All patches released by a vendor are important enough to have a close look if you use the affected systems. There is little incentive for vendors to publicize patches that do not have some form of risk to them
Keywords: mspatchday
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