oCERT-2009-001 Pango integer overflow in heap allocation size calculations


Pango is a library for laying out and rendering text, with an emphasis on internationalization. Pango suffers from a multiplicative integer overflow which may lead to a potentially exploitable, heap overflow depending on the calling conditions. For example, this vulnerability is remotely reachable in Firefox by creating an overly large document.location value but only results in a process-terminating, allocation error (denial of service).

The affected function is pango_glyph_string_set_size. An overflow check when doubling the size neglects the overflow possible on the subsequent allocation:

  string->glyphs = g_realloc (string->glyphs, string->space *
                              sizeof (PangoGlyphInfo));

Note that other font rendering subsystems suffer from similar issues and should be cross-checked by maintainers.

Affected version:

Pango < 1.24

(check with your Ñ•pecific package maintainer for backports)

Fixed version:

Pango >= 1.24

Credit: Will Drewry, oCERT Team | Google Security Team. Special thanks to Karl Tomlinson for extended analysis of the impact on Firefox.

CVE: CVE-2009-1194


2009-02-22: attempted to contact upstream via gtk-i18n-list AT gnome.org
2009-02-25: bug filed with Mozilla against firefox
2009-03-02: Behdad Esfahbod patched Pango upstream (for 1.24)
2009-04-13: vendor-sec alerted regarding backporting the silent pango fix
2009-04-23: embargo date and CVE assigned (thanks Josh Bressers!)
2009-05-07: advisory release