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Mozilla Foundation Security Advisory 2016-14

Vulnerabilities in Graphite 2

February 11, 2016
Holger Fuhrmannek
Firefox ESR, Thunderbird
Fixed in
  • Firefox ESR 38.6.1
  • Thunderbird 38.6


Security researcher Holger Fuhrmannek reported that a malicious Graphite "smart font" could circumvent the validation of internal instruction parameters in the Graphite 2 library using special CNTXT_ITEM instructions. This could result in arbitrary code execution.

This issue affected Graphite 2 version 1.3.4, which was used in the Firefox ESR branch. To address this issue and other security vulnerabilities recently disclosed by Cisco Talos affecting this version of the library, Firefox ESR has been updated to version 1.3.5, the same one used in Firefox 44.

In general this flaw cannot be exploited through email in the Thunderbird product, but is potentially a risk in browser or browser-like contexts.