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Mozilla Foundation Security Advisory 2016-77

Buffer overflow in ClearKey Content Decryption Module (CDM) during video playback

August 2, 2016
Firefox, Firefox ESR
Fixed in
  • Firefox 48
  • Firefox ESR 45.3


An anonymous security researcher working with Trend Micro's Zero Day Initiative reported a buffer overflow in the ClearKey Content Decryption Module (CDM) used by the Encrypted Media Extensions (EME) API. This vulnerability can be triggered using a malformed video file due to incorrect error handling. This could allow arbitrary code execution if combined with a second vulnerability that allows an escape from the Gecko Media Plugin (GMP) sandbox. Without such a vulnerability, the buffer overflow is contained within the GMP sandbox and cannot be exploited.