The vulnerable system is bound to the network stack and the set of possible attackers extends beyond the other options listed below, up to and including the entire Internet. Such a vulnerability is often termed “remotely exploitable” and can be thought of as an attack being exploitable at the protocol level one or more network hops away (e.g., across one or more routers). An example of a network attack is an attacker causing a denial of service by sending a specially crafted TCP packet across a wide area network (e.g., CVE-2004-0230).
Attack Complexity
Low
AC
The attacker must take no measurable action to exploit the vulnerability. The attack requires no target-specific circumvention to exploit the vulnerability. An attacker can expect repeatable success against the vulnerable system.
Privileges Required
None
PR
The attacker is unauthenticated prior to attack, and therefore does not require any access to settings or files of the vulnerable system to carry out an attack.
User Interaction
None
UI
The vulnerable system can be exploited without interaction from any human user, other than the attacker. Examples include: a remote attacker is able to send packets to a target system a locally authenticated attacker executes code to elevate privileges
Scope
Unchanged
S
An exploited vulnerability can only affect resources managed by the same security authority. In the case of a vulnerability in a virtualized environment, an exploited vulnerability in one guest instance would not affect neighboring guest instances.
Confidentiality
High
C
There is total information disclosure, resulting in all data on the system being revealed to the attacker, or there is a possibility of the attacker gaining control over confidential data.
Integrity
High
I
There is a total compromise of system integrity. There is a complete loss of system protection, resulting in the attacker being able to modify any file on the target system.
Availability
High
A
There is a total shutdown of the affected resource. The attacker can deny access to the system or data, potentially causing significant loss to the organization.
Good morning,
This might not come as a surprise, but there appears to be a *very*
interesting and apparently very much exploitable overflow in Microsoft
Internet Explorer (mshtml.dll).
This vulnerability can be triggered by specifying more than a couple
thousand script action handlers (such as onLoad, onMouseMove, etc) for any
single HTML tag. Due to a programming error, MSIE will then attempt to
write memory array out of bounds, at an offset corresponding to the ID of
the script action handler multiplied by 4 (due to 32-bit address clipping,
the result is a small positive integer).
The list of IDs can be found on the Web, and is as follows (values in
parentheses = resulting offsets):
onhelp = 0x8001177d (+0x45df4)
onclick = 0x80011778 (+0x45de0)
ondblclick = 0x80011779 (+0x45de4)
onkeyup = 0x80011776 (+0x45dd8)
onkeydown = 0x80011775 (+0x45dd4)
onkeypress = 0x80011777 (+0x45ddc)
onmouseup = 0x80011773 (+0x45dcc)
onmousedown = 0x80011772 (+0x45dc8)
onmousemove = 0x80011774 (+0x45dd0)
onmouseout = 0x80011771 (+0x45dc4)
onmouseover = 0x80011770 (+0x45dc0)
onreadystatechange = 0x80011789 (+0x45e24)
onafterupdate = 0x80011786 (+0x45e18)
onrowexit = 0x80011782 (+0x45e08)
onrowenter = 0x80011783 (+0x45e0c)
ondragstart = 0x80011793 (+0x45e4c)
onselectstart = 0x80011795 (+0x45e54)
What happens next depends on the structure of the page in which the
malicious tag is embedded, as well as previously visited page and
previously initialized extensions (all these factors can be controlled by
the attacker).
When the offending page contains no additional elements, and the user is
not redirected from elsewhere, the browser will typically crash
immediately, because there is no allocated memory at the resulting offset.
In all other cases, crashes will typically occur later, due to attempted
use of unrelated but corrupted in-memory buffers -for example, when the
user attempts to leave or reload the page. Another good example is coming
from a page that contains Macromedia Flash - this usually causes the Flash
plugin itself to choke on corrupted memory on cleanup.
For non-believers, there's a short but fiery demonstration page available
at http://lcamtuf.coredump.cx/iedie.html (yes, it will probably crash your
browser).
Tested on MSIE 6.0.2900.2180.xpsp2.040806-1825 on Windows XP SP2. As far
as I can tell, other browser makes (Firefox, Opera) are not susceptible to
this attack.
I eagerly await due reprimend from Microsoft for not disclosing this
vulnerability in a manner that benefits them most, not passing start, not
collecting $200 (from iDefense?).
Regards,
/mz
http://lcamtuf.coredump.cx/silence/
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