Bug#960527: libcroco: CVE-2020-12825

[Salvatore Bonaccorso]

Hi Simon,

On Wed, May 13, 2020 at 05:02:32PM +0100, Simon McVittie wrote:
> 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.

Thanks for your analysis and overview. FWIW, the issue was marked
earlier no-dsa for stretch and buster, so if/whenever a fix arise
might be enough to adress it via a point release.

Regards,
Salvatore