Fb has patched a important vulnerability within the Fb Messenger for Android cellular app, which might have let attackers spy on different Fb customers utilizing audio and video calls.
Natalie Silvanovich, the researcher with Google’s Venture Zero who found the bug, says it existed in Fb Messenger’s implementation of a protocol referred to as WebRTC, which the app makes use of to arrange audio and video calls by exchanging “thrift messages” between callee and caller.
Usually, an individual receiving a name does not ship audio till the decision is accepted, Silvanovich stated in a write-up of her findings. This step is carried out by both not calling setLocalDescription till the callee has clicked settle for, or by setting audio and video media description within the native Session Description Protocol (SDP) to inactive and updating them when the decision is accepted.
Nevertheless, she wrote, there’s a message sort referred to as SdpUpdate, which isn’t used for name setup and can trigger setLocalDescription to be referred to as instantly. If this message is shipped to somebody whereas their cellphone is ringing, the callee would start to transmit audio instantly and allow an attacker to take heed to their environment. The callee wouldn’t must reply their cellphone.
Silvanovich explains the steps of an assault in her report. In a separate write-up celebrating the 10th anniversary of its bug bounty program, Fb famous an attacker would want to have sure permissions, corresponding to already being Fb buddies, to name a sufferer. The attacker would additionally want to make use of reverse engineering instruments to ship a customized message from their Messenger app.
Fb fastened the vulnerability with a server-side patch and says its researchers utilized extra protections for this concern throughout apps that use the identical protocol for one-on-one calls. The flaw merited a bug bounty of $60,000, among the many three highest bug bounties the corporate provides.
Learn Silvanovich’s Venture Zero bug report for extra particulars.
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