23-Year-Old X11 Server Security Vulnerability Discovered

An anonymous reader writes "The recent report of X11/X.Org security in bad shape rings more truth today. The X.Org Foundation announced today that they've found a X11 security issue that dates back to 1991. The issue is a possible stack buffer overflow that could lead to privilege escalation to root and affects all versions of the X Server back to X11R5. After the vulnerability being in the code-base for 23 years, it was finally uncovered via the automated cppcheck static analysis utility." There's a scanf used when loading BDF fonts that can overflow using a carefully crafted font. Watch out for those obsolete early-90s bitmap fonts.

Many eyes...

[Anonymous Coward]

...looking elsewhere.

Re:Many eyes...

[i kan reed]

The real trick of the "With enough eyes all bugs are shallow" is that the function for "enough eyes" is exponential with respect to lines of code, and open source projects don't actually hit it.

Re:Privilege escalation is to the server credentia

[i kan reed]

Root isn't the only kind of vulnerability. Seizing control of peoples' UIs is a pretty big deal(especially as far as phishing or keylogging goes).

Re:Many eyes...

[grub]

"Many eyes" is bogus, "the right eyes" is more appropriate.

Re:scary

[Anonymous Coward]

Given that you need to be using obsolete 90s bitmap fonts for this to be an issue, and that X11/X.org is never run as root, I'm not sure that "scary" is the word for this (there's a reason it hasn't come up before in the 23 years since it was introduced).

Nonetheless, I'll be upgrading my X.org package just for thoroughness.

Re:scary

[Anonymous Coward]

Hasn't come up before? The Snowden docs suggest the NSA has been using this (and/or other X bugs) for years.

Re:scary

[buchner.johannes]

Given that you need to be using obsolete 90s bitmap fonts for this to be an issue, and that X11/X.org is never run as root, I'm not sure that "scary" is the word for this (there's a reason it hasn't come up before in the 23 years since it was introduced).

Correct in principle, except for two remarks:

• X runs as root, and has always. Just like getty.
• If you craft a new bitmap font, running "xset fp+" as a user has the potential to gain you root privileges.

So yes, not "scary". Just a critical security bug.

Re:Many eyes...

[hawkinspeter]

I'd recommend running the same tool (cppcheck) on the Windows source code before trying to be ironic.

Re:scary

[PPH]

Right. And this is why its so important to have the source code available. Some argue, "Who actually looks at this stuff?" Well, here's an example of someone who did. Not in the classical sense of some aspie code geek reading it by hand. But just feed it to some automated tools and see what pops out.

Re:Many eyes...

[i kan reed]

It should include bogus fonts with randomized data to test for crashes, data validation, and the like, yes.