Package Instance

Multiple vulnerabilities in libxml2, libxslt
The vendored libxml2 and libxslt libraries have multiple vulnerabilities: CVE-2015-1819 CVE-2015-7941_1 CVE-2015-7941_2 CVE-2015-7942 CVE-2015-7942-2 CVE-2015-8035 CVE-2015-7995

Nokogiri::XML::Schema trusts input by default, exposing risk of an XXE vulnerability
### Description

In Nokogiri versions <= 1.11.0.rc3, XML Schemas parsed by `Nokogiri::XML::Schema`
are **trusted** by default, allowing external resources to be accessed over the
network, potentially enabling XXE or SSRF attacks.

This behavior is counter to
the security policy followed by Nokogiri maintainers, which is to treat all input
as **untrusted** by default whenever possible.

Please note that this security
fix was pushed into a new minor version, 1.11.x, rather than a patch release to
the 1.10.x branch, because it is a breaking change for some schemas and the risk
was assessed to be "Low Severity".

### Affected Versions

Nokogiri `<= 1.10.10` as well as prereleases `1.11.0.rc1`, `1.11.0.rc2`, and `1.11.0.rc3`

### Mitigation

There are no known workarounds for affected versions. Upgrade to Nokogiri
`1.11.0.rc4` or later.

If, after upgrading to `1.11.0.rc4` or later, you wish
to re-enable network access for resolution of external resources (i.e., return to
the previous behavior):

1. Ensure the input is trusted. Do not enable this option
for untrusted input.
2. When invoking the `Nokogiri::XML::Schema` constructor,
pass as the second parameter an instance of `Nokogiri::XML::ParseOptions` with the
`NONET` flag turned off.

So if your previous code was:

``` ruby
# in v1.11.0.rc3 and earlier, this call allows resources to be accessed over the network
# but in v1.11.0.rc4 and later, this call will disallow network access for external resources
schema = Nokogiri::XML::Schema.new(schema)

# in v1.11.0.rc4 and later, the following is equivalent to the code above
# (the second parameter is optional, and this demonstrates its default value)
schema = Nokogiri::XML::Schema.new(schema, Nokogiri::XML::ParseOptions::DEFAULT_SCHEMA)
```

Then you can add the second parameter to indicate that the input is trusted by changing it to:

``` ruby
# in v1.11.0.rc3 and earlier, this would raise an ArgumentError
# but in v1.11.0.rc4 and later, this allows resources to be accessed over the network
schema = Nokogiri::XML::Schema.new(trusted_schema, Nokogiri::XML::ParseOptions.new.nononet)
```

Improper Input Validation
In `numbers.c` in libxslt, which is used by nokogiri, an `xsl:number` with certain format strings could lead to an uninitialized read in `xsltNumberFormatInsertNumbers`. This could allow an attacker to discern whether a byte on the stack contains the characters `[AaIi0]`, or any other character.

NULL Pointer Dereference
A NULL pointer dereference vulnerability exists in the xpath.c:xmlXPathCompOpEval() function of libxml2 when parsing an invalid XPath expression in the XPATH_OP_AND or XPATH_OP_OR case. Applications processing untrusted XSL format inputs with the use of the libxml2 library may be vulnerable to a denial of service attack due to a crash of the application.