Code: char **XGetFontPath(
    register Display *dpy,
    int *npaths)	/* RETURN */
{
	xGetFontPathReply rep;
	unsigned long nbytes = 0;
	char **flist = NULL;
	char *ch = NULL;
	char *chend;
	int count = 0;
	register unsigned i;
	register int length;
	_X_UNUSED register xReq *req;

	LockDisplay(dpy);
	GetEmptyReq (GetFontPath, req);
	(void) _XReply (dpy, (xReply *) &rep, 0, xFalse);

	if (rep.nPaths) {
	    flist = Xmalloc(rep.nPaths * sizeof (char *));
	    if (rep.length < (INT_MAX >> 2)) {
		nbytes = (unsigned long) rep.length << 2;
		ch = Xmalloc (nbytes + 1);
                /* +1 to leave room for last null-terminator */
	    }

	    if ((! flist) || (! ch)) {
		Xfree(flist);
		Xfree(ch);
		_XEatDataWords(dpy, rep.length);
		UnlockDisplay(dpy);
		SyncHandle();
		return (char **) NULL;
	    }

	    _XReadPad (dpy, ch, nbytes);
	    /*
 	     * unpack into null terminated strings.
 	     */
 	    chend = ch + nbytes;
	    length = *ch;
 	    for (i = 0; i < rep.nPaths; i++) {
 		if (ch + length < chend) {
 		    flist[i] = ch+1;  /* skip over length */
 		    ch += length + 1; /* find next length ... */
		    length = *ch;
 		    *ch = '\0'; /* and replace with null-termination */
 		    count++;
 		} else
		    flist[i] = NULL;
	    }
	}
	*npaths = count;
	UnlockDisplay(dpy);
	SyncHandle();
	return (flist);
}

Vulnerability Type: Exec Code
CWE ID: CWE-787
Summary: An issue was discovered in libX11 through 1.6.5. The function XListExtensions in ListExt.c interprets a variable as signed instead of unsigned, resulting in an out-of-bounds write (of up to 128 bytes), leading to DoS or remote code execution.
Commit Message: 