Two recently announced vulnerabilities in BlackBerry Enterprise Server permit a malicious attack that can disrupt the flow of information between Enterprise Server and BlackBerry Router or prevent users from being able to open email attachments, the system's developer, RIM (Research in Motion), said yesterday.

The first vulnerability allows an attacker to use a corrupt Tiff image file to cause a heap overflow error that can stop a user's ability to view attachments, RIM said. The vulnerability was demonstrated on 30 December by FX of security group Phenoelit at the 22nd Chaos Communication Conference in Berlin. That day, US-CERT (the US Computer Emergency Readiness Team) issued an advisory noting the existence of the vulnerability and referred users to RIM for remediation.

In a posting on its support website, RIM said it was aware of the vulnerability and will fix the problem in future releases of BlackBerry Enterprise Server. In the meantime, the company suggested that administrators use a workaround that blocks Tiff attachments.

The second vulnerability was also demonstrated at the Chaos Communication Conference and noted by US-CERT. This vulnerability is exploited by sending malformed protocol packets that cause a denial of service for all BlackBerry Enterprise Server communication. This vulnerability normally applies only to internal users but can be exploited by an external attacker who is able to manipulate DNS (Domain Name System) queries, RIM said.

The company advised customers to ensure that the BlackBerry Enterprise Server and BlackBerry Router are behind a properly configured firewall to protect them from external attacks. It also advised companies to create static entries in their DNS or hosts tables for the BlackBerry Infrastructure to minimise the risk of DNS hijacking.

RIM said in a statement: "RIM has already developed software fixes for the issues identified by FX. Although there have been no reports of any actual problems by customers, RIM has also provided precautionary measures that can be taken in the meantime until customers implement the software updates."

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