Microsoft issued an emergency patch on June 3, acknowledging reports that a simple eight-character string could crash the program on certain platforms.
On June 2, Skype users on the product's community forums reported that sending a simple string—http://:—could crash the Skype client on Windows and Android platforms. The issue resulted from the improper handling of a malformed Web address, according to one user. When the Skype client attempts to process the message, the act crashes the program, users reported.
"It looks like the program attempts to read from protected memory space and the Windows kernel stops it," user "PORT_1337" stated.
The crash bug appears quite similar to an issue that affected Apple's own instant messaging application, Messages. On May 27, security researchers discovered that a text message combining English and Arabic text in a Unicode-encoded message could crash iOS devices and cause problems on Mac OS X systems. Many users sent the crash bug as a prank to their friends, resulting in more than a million messages sent to users over the course of a day.
In the most recent case, Skype users informed Microsoft of the crash issue, which reportedly caused the messaging and voice-over-IP application to shut down. Because restarting the program merely reloaded the problematic message, Skype would continue to crash until the user who sent the message deleted it.
Microsoft confirmed the bug and released an update for the issue on June 3.
"We are aware of a problem that was causing Skype clients to crash," Microsoft stated in a post on the Skype forums. "Our engineering teams worked hard to resolve this issue, and have released updates for all impacted Skype platforms."
The error message generated by the Skype program when it crashes appears to indicate that the application encounters a logic error when it parses the text, Chris Wysopal, chief technology officer for code-security firm Veracode, stated in an email response to eWEEK queries.
"A fuzzer would have likely found this, but it shows a poor security testing process in general," he said. "Malformed URLs are a basic test input for QA [quality-assurance] testing."
When an input crashes an application, there is a chance that the revealed vulnerability could be exploited by an attacker to run code on the affected system. In the case of the Skype bug, however, there is only a slight chance that an attacker could take control of the system, Wysopal said.
"Given this is a read error, unless the attacker can control the location where the read occurs, it is unlikely this is remotely exploitable," he stated. "A remote exploit would be extremely bad, given the wormable nature of messaging software."
Apple confirmed that a fix is in the works for its own messaging issue, but has not yet released a patch for Messages.