A vulnerability was found in libX11 due to an integer overflow within the XCreateImage() function. This flaw allows a local user to trigger an integer overflow and execute arbitrary code with elevated privileges.

A vulnerability was found in libX11 due to an infinite loop within the PutSubImage() function. This flaw allows a local user to consume all available system resources and cause a denial of service condition.

A vulnerability was found in libX11 due to a boundary condition within the _XkbReadKeySyms() function. This flaw allows a local user to trigger an out-of-bounds read error and read the contents of memory on the system.

A vulnerability was found in libX11. The security flaw occurs because the functions in src/InitExt.c in libX11 do not check that the values provided for the Request, Event, or Error IDs are within the bounds of the arrays that those functions write to, using those IDs as array indexes. They trust that they were called with values provided by an Xserver adhering to the bounds specified in the X11 protocol, as all X servers provided by X.Org do. As the protocol only specifies a single byte for these values, an out-of-bounds value provided by a malicious server (or a malicious proxy-in-the-middle) can only overwrite other portions of the Display structure and not write outside the bounds of the Display structure itself, possibly causing the client to crash with this memory corruption.

LookupCol.c in X.Org X through X11R7.7 and libX11 before 1.7.1 might allow remote attackers to execute arbitrary code. The libX11 XLookupColor request (intended for server-side color lookup) contains a flaw allowing a client to send color-name requests with a name longer than the maximum size allowed by the protocol (and also longer than the maximum packet size for normal-sized packets). The user-controlled data exceeding the maximum size is then interpreted by the server as additional X protocol requests and executed, e.g., to disable X server authorization completely. For example, if the victim encounters malicious terminal control sequences for color codes, then the attacker may be able to take full control of the running graphical session.

An integer overflow vulnerability leading to a double-free was found in libX11. This flaw allows a local privileged attacker to cause an application compiled with libX11 to crash, or in some cases, result in arbitrary code execution. The highest threat from this flaw is to confidentiality, integrity as well as system availability.

An integer overflow leading to a heap-buffer overflow was found in The X Input Method (XIM) client was implemented in libX11 before version 1.6.10. As per upstream this is security relevant when setuid programs call XIM client functions while running with elevated privileges. No such programs are shipped with Red Hat Enterprise Linux.