Severity
Nokogiri maintainers have evaluated this as Low Severity (CVSS3 2.6).
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):
- Ensure the input is trusted. Do not enable this option for untrusted input.
- 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:
# 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:
# 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)
References
Credit
This vulnerability was independently reported by @eric-therond and @gucki.
The Nokogiri maintainers would like to thank HackerOne for providing a secure, responsible mechanism for reporting, and for providing their fantastic service to us.
References
eric-therond Analyst
Severity
Nokogiri maintainers have evaluated this as Low Severity (CVSS3 2.6).
Description
In Nokogiri versions <= 1.11.0.rc3, XML Schemas parsed by
Nokogiri::XML::Schemaare 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
<= 1.10.10as well as prereleases1.11.0.rc1,1.11.0.rc2, and1.11.0.rc3Mitigation
There are no known workarounds for affected versions. Upgrade to Nokogiri
1.11.0.rc4or later.If, after upgrading to
1.11.0.rc4or later, you wish to re-enable network access for resolution of external resources (i.e., return to the previous behavior):Nokogiri::XML::Schemaconstructor, pass as the second parameter an instance ofNokogiri::XML::ParseOptionswith theNONETflag turned off.So if your previous code was:
Then you can add the second parameter to indicate that the input is trusted by changing it to:
References
Credit
This vulnerability was independently reported by @eric-therond and @gucki.
The Nokogiri maintainers would like to thank HackerOne for providing a secure, responsible mechanism for reporting, and for providing their fantastic service to us.
References