Microsoft said it won't be fixing or is pushing patches to a later date for three of the four security flaws uncovered in its Teams business communication platform earlier this March.
The disclosure comes from Berlin-based cybersecurity firm Positive Security, which found that the implementation of the link preview feature was susceptible to a number of issues that could "allow accessing internal Microsoft services, spoofing the link preview, and, for Android users, leaking their IP address, and DoS'ing their Teams app/channels."
Of the four vulnerabilities, Microsoft is said to have addressed only one that results in IP address leakage from Android devices, with the tech giant noting that a fix for the denial-of-service (DoS) flaw will be considered in a future version of the product. The issues were responsibly disclosed to the company on March 10, 2021.
Chief among the flaws is a server-side request forgery (SSRF) vulnerability in the endpoint "/urlp/v1/url/info" that could be exploited to glean information from Microsoft's local network. Also discovered is a spoofing bug wherein the preview link target can be altered to point to any malicious URL while keeping the main link, preview image and description intact, allowing attackers to hide malicious links and stage improved phishing attacks.
The DoS vulnerability, which affects the Android version of Teams, could cause the app to crash simply by sending a message with a specially crafted link preview containing an invalid target instead of a legitimate URL. The last of the issues concerns an IP address leak, which also affects the Android app. By intercepting messages that include a link preview to point the thumbnail URL to a non-Microsoft domain, Positive Security said it's possible to gain access to a user's IP address and user agent data.
"While the discovered vulnerabilities have a limited impact, it's surprising both that such simple attack vectors have seemingly not been tested for before, and that Microsoft does not have the willingness or resources to protect their users from them," Positive Security's co-founder Fabian Bräunlein said.