Bug 285991 (CVE-2007-4730)

Summary: CVE-2007-4730 X.org composite extension buffer overflow
Product: [Other] Security Response Reporter: Josh Bressers <bressers>
Component: vulnerabilityAssignee: Red Hat Product Security <security-response-team>
Status: CLOSED ERRATA QA Contact:
Severity: medium Docs Contact:
Priority: medium    
Version: unspecifiedCC: kreilly, xgl-maint
Target Milestone: ---Keywords: Security
Target Release: ---   
Hardware: All   
OS: Linux   
URL: http://bugs.freedesktop.org/show_bug.cgi?id=7447
Fixed In Version: Doc Type: Bug Fix
Doc Text:
Story Points: ---
Clone Of: Environment:
Last Closed: 2007-10-26 09:16:28 UTC Type: ---
Regression: --- Mount Type: ---
Documentation: --- CRM:
Verified Versions: Category: ---
oVirt Team: --- RHEL 7.3 requirements from Atomic Host:
Cloudforms Team: --- Target Upstream Version:
Bug Depends On: 286051, 286061, 286071, 286081, 286091, 286101, 286111    
Bug Blocks:    

Description Josh Bressers 2007-09-11 14:01:10 UTC
A buffer overflow flaw has been found in the X.org composite extension.  The
upstream bug has more details:


By running a server at depth 16, it becomes possible for a local user to
overflow a buffer by creating a window with depth 32, then resizing it.

Comment 2 Søren Sandmann Pedersen 2007-09-11 19:15:15 UTC
FC6, F7, Fdevel, and rhels 5.0.z, 5.1 are not vulnerable because of this patch:

localhost:~/vertigo/rpms/xorg-x11-server/RHEL-5% cat
Disable backfilling of windows created with bg=none, which otherwise
would force a framebuffer readback.

--- ./composite/compalloc.c.spiffiffity 2006-03-13 16:59:55.000000000 -0500
+++ ./composite/compalloc.c     2006-04-12 16:37:50.000000000 -0400
@@ -478,6 +478,7 @@
      * Copy bits from the parent into the new pixmap so that it will
      * have "reasonable" contents in case for background None areas.
+#if 0
     if (pGC)
        XID val = IncludeInferiors;
@@ -492,6 +493,7 @@
                               w, h, 0, 0);
        FreeScratchGC (pGC);
     return pPixmap;

Comment 3 Josh Bressers 2007-09-18 11:55:22 UTC
We are changing the severity here to moderate. Here is some additional
information provided by Adam Jackson:

- the Composite extension is not enabled by default in RHEL4, so the user
  would have had to go out of their way to turn it on.
- we don't ship any compositing manager in RHEL4, so they'd need to have
  installed one.
- the exploit requires the ability to authenticate to the X server, so the
  attacker would need to have already gained rights equivalent to the user.

Comment 4 Tomas Hoger 2007-10-26 09:16:28 UTC
For Red Hat Enterprise Linux 4, this issue was addressed in RHSA-2007:0898:


Red Hat Enterprise Linux 5 and current versions of Fedora were not affected as
described in comment #2.