Bug#960527: libcroco: CVE-2020-12825

[Simon McVittie]

On Wed, 13 May 2020 at 17:21:44 +0200, Salvatore Bonaccorso wrote:
> CVE-2020-12825[0]:
> | libcroco through 0.6.13 has excessive recursion in
> | cr_parser_parse_any_core in cr-parser.c, leading to stack consumption.

Mitigation: here are the only things in >= stable that depend on libcroco:

- gnome-shell, cinnamon: I don't think these parse untrusted CSS, only
  CSS that comes from GNOME Shell itself or a Shell extension (which can
  execute arbitrary code with the user's privileges *anyway*, so they're
  inherently trusted).

  gnome-shell in unstable contains a cut-down fork of croco, in which
  the developers are deleting unused code and redoing what's left in Rust,
  using Mozilla's underlying parser; similar reasoning applies to that.

  cinnamon is basically a fork of an old version of GNOME Shell, so it's
  still using libcroco.

- gettext: seems to be part of term-styled-ostream, an ANSI terminal text
  highlighting library[1], rather than parsing anything untrusted.

  There is a vendored copy included, but Debian uses the system copy.

- librsvg in stable

  In unstable, librsvg was rewritten in Rust, using Mozilla's underlying
  parser.

- libccss in stable

  This package is unmaintained upstream and was removed from
  testing/unstable.

(I suspect the GNOME team might end up orphaning libcroco, now that no
GNOME components depend on it any more.)

I think the only one of those that's potentially of interest from the
point of view of denial-of-service in a long-running process is librsvg in
stable, and even that seems more likely to be used as a batch-mode tool,
via imagemagick or rsvg-convert(1) or similar.

    smcv

[1] Yes, really.