CVE-2015-1802

La función bdfReadProperties en bitmap/bdfread.c en X.Org libXfont anterior a 1.4.9 y 1.5.x anterior a 1.5.1 permite a usuarios remotos autenticados causar una denegación de servicio (escritura y caída fuera de rango) o la posibilidad de ejecutar código arbitrario a través de (1) negative o (2) large property count en un archivo de fuente BDF.

An integer overflow flaw was found in the way libXfont processed certain Glyph Bitmap Distribution Format (BDF) fonts. A malicious, local user could use this flaw to crash the X.Org server or, potentially, execute arbitrary code with the privileges of the X.Org server.

Ilja van Sprundel discovered that libXfont incorrectly handled font metadata file parsing. A local attacker could use this issue to cause libXfont to crash, or possibly execute arbitrary code in order to gain privileges. Ilja van Sprundel discovered that libXfont incorrectly handled X Font Server replies. A malicious font server could return specially-crafted data that could cause libXfont to crash, or possibly execute arbitrary code. The bdf parser reads a count for the number of properties defined in a font from the font file, and allocates arrays with entries for each property based on that count. It never checked to see if that count was negative, or large enough to overflow when multiplied by the size of the structures being allocated, and could thus allocate the wrong buffer size, leading to out of bounds writes. If the bdf parser failed to parse the data for the bitmap for any character, it would proceed with an invalid pointer to the bitmap data and later crash when trying to read the bitmap from that pointer. The bdf parser read metrics values as 32-bit integers, but stored them into 16-bit integers. Overflows could occur in various operations leading to out-of-bounds memory access.