CVE-2020-26247

Nokogiri is a Rubygem providing HTML, XML, SAX, and Reader parsers with XPath and CSS selector support. In Nokogiri before version 1.11.0.rc4 there is an XXE vulnerability. 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. This is fixed in Nokogiri version 1.11.0.rc4.

Nokogiri is a Rubygem providing HTML, XML, SAX, and Reader parsers with XPath and CSS selector support. In Nokogiri before version 1.11.0.rc4 there is an XXE vulnerability. 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. This is fixed in Nokogiri version 1.11.0.rc4.

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):

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:

# 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

• This issue's public advisory
• Original Hackerone report (private)
• OWASP description of XXE attack
• OWASP description of SSRF attack

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.

Nokogiri parses and searches XML/HTML very quickly, and also has correctly implemented CSS3 selector support as well as XPath support. Nokogiri also features an Hpricot compatibility layer to help ease the change to using correct CSS and XPath.

Security Fix(es):

Nokogiri is a Rubygem providing HTML, XML, SAX, and Reader parsers with XPath and CSS selector support. In Nokogiri before version 1.11.0.rc4 there is an XXE vulnerability. 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. This is fixed in Nokogiri version 1.11.0.rc4.(CVE-2020-26247)

Nokogiri is a Rubygem providing HTML, XML, SAX, and Reader parsers with XPath and CSS selector support. In Nokogiri before version 1.11.0.rc4 there is an XXE vulnerability. 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. This is fixed in Nokogiri version 1.11.0.rc4.

A command injection vulnerability in Nokogiri v1.10.3 and earlier allows commands to be executed in a subprocess via Ruby's Kernel.open method. Processes are vulnerable only if the undocumented method Nokogiri::CSS::Tokenizer#load_file is being called with unsafe user input as the filename (CVE-2019-5477).

In Nokogiri before version 1.11.0.rc4 there is an XXE vulnerability. 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 (CVE-2020-26247).

The ruby-nokogiri package has been updated to version 1.10.10 to fix CVE-2019-5477 and patched to fix CVE-2020-26247.

This update for rubygem-nokogiri fixes the following issues:

rubygem-nokogiri was updated to 1.8.5 (bsc#1156722).

Security issues fixed:

• CVE-2019-5477: Fixed a command injection vulnerability (bsc#1146578).
• CVE-2020-26247: Fixed an XXE vulnerability in Nokogiri::XML::Schema (bsc#1180507).

This update was imported from the SUSE:SLE-15:Update update project.

This update for rubygem-nokogiri fixes the following issues:

• CVE-2019-5477: Fixed a command injection vulnerability (bsc#1146578).
• CVE-2020-26247: Fixed an XXE vulnerability in Nokogiri::XML::Schema (bsc#1180507).

This update for rubygem-nokogiri fixes the following issues:

rubygem-nokogiri was updated to 1.8.5 (bsc#1156722).

Security issues fixed:

• CVE-2019-5477: Fixed a command injection vulnerability (bsc#1146578).
• CVE-2020-26247: Fixed an XXE vulnerability in Nokogiri::XML::Schema (bsc#1180507).

This update for ardana-cobbler, cassandra, cassandra-kit, crowbar-core, crowbar-openstack, documentation-suse-openstack-cloud, grafana, kibana, openstack-heat-templates, openstack-monasca-installer, openstack-nova, python-Django, python-elementpath, python-eventlet, python-py, python-pysaml2, python-six, python-xmlschema fixes the following issues:

Security fixes included on this update:

cassandra-kit:

• CVE-2020-17516: Internode encryption enforcement vulnerability

cassandra:

• CVE-2020-17516: Internode encryption enforcement vulnerability
• CVE-2017-5929 logback: Fixed a serialization vulnerability in SocketServer and ServerSocketReceiver

crowbar-core: CVE-2020-26247: Potentially XXE or SSRF attacks by parsed Nokogiri::XML::Schema

grafana:

• CVE-2021-27358: Unauthenticated remote attackers to trigger a Denial of Service via a remote API call

kibana:

• CVE-2017-11481: Fixed an XSS via URL fields
• CVE-2017-11499: Fixed a constant hashtable seeds vulnerability

python-Django:

• CVE-2021-28658: Potential directory-traversal via uploaded files
• CVE-2021-31542: Potential directory-traversal via uploaded files
• CVE-2021-33203: Potential directory traversal via admindocs
• CVE-2021-33571: Possible indeterminate SSRF, RFI, and LFI attacks since validators accepted leading zeros in IPv4 addresses
• CVE-2021-23336: Fixed web cache poisoning via django.utils.http.limited_parse_qsl

python-eventlet:

• CVE-2021-21419: Improper handling of highly compressed data and memory allocation with excessive size value

python-pysaml2:

• CVE-2021-21238: Fixed an improper verification of cryptographic signatures for signed SAML documents
• CVE-2021-21239: Fixed an improper verification of cryptographic signatures when using CryptoBackendXmlSec1()_

python-py:

• CVE-2020-29651: Regular expression denial of service in svnwc.py

rubygem-activerecord-session_store:

• CVE-2019-25025: Fixed a hijack sessions by using timing attacks targeting the session id CVE-2019-16782

Non-security fixes included on this update:

Changes in ardana-cobbler:

• Update to version 8.0+git.1614096566.e8c2b27:
  • Change install_recommended to true (bsc#1181828)

Changes in cassandra:

• update to 3.11.10 (bsc#1181689, CVE-2020-17516)

• Fix digest computation for queries with fetched but non queried columns (CASSANDRA-15962)
• Reduce amount of allocations during batch statement execution (CASSANDRA-16201)
• Update jflex-1.6.0.jar to match upstream (CASSANDRA-16393)
• Fix DecimalDeserializer#toString OOM (CASSANDRA-14925)
• Rate limit validation compactions using compaction_throughput_mb_per_sec (CASSANDRA-16161)
• SASI's max_compaction_flush_memory_in_mb settings over 100GB revert to default of 1GB (CASSANDRA-16071)
• Prevent unbounded number of pending flushing tasks (CASSANDRA-16261)
• Improve empty hint file handling during startup (CASSANDRA-16162)
• Allow empty string in collections with COPY FROM in cqlsh (CASSANDRA-16372)
• Fix skipping on pre-3.0 created compact storage sstables due to missing primary key liveness (CASSANDRA-16226)
• Extend the exclusion of replica filtering protection to other indices instead of just SASI (CASSANDRA-16311)
• Synchronize transaction logs for JBOD (CASSANDRA-16225)
• Fix the counting of cells per partition (CASSANDRA-16259)
• Fix serial read/non-applying CAS linearizability (CASSANDRA-12126)
• Avoid potential NPE in JVMStabilityInspector (CASSANDRA-16294)
• Improved check of num_tokens against the length of initial_token (CASSANDRA-14477)
• Fix a race condition on ColumnFamilyStore and TableMetrics (CASSANDRA-16228)
• Remove the SEPExecutor blocking behavior (CASSANDRA-16186)
• Fix invalid cell value skipping when reading from disk (CASSANDRA-16223)
• Prevent invoking enable/disable gossip when not in NORMAL (CASSANDRA-16146)
• Wait for schema agreement when bootstrapping (CASSANDRA-15158)
• Fix the histogram merge of the table metrics (CASSANDRA-16259)
• Synchronize Keyspace instance store/clear…

It was discovered Nokogiri did not correctly parse XML Schemas. If a user or automated system were tricked into opening a specially crafted file, an attacker could possibly use this issue to execute arbitrary code. This issue only affected Ubuntu 20.04 LTS. (CVE-2020-26247)

Agustin Gianni discovered that Nokogiri did not correctly parse XML and HTML files. If a user or automated system were tricked into opening a specially crafted file, an attacker could possibly use this issue to cause a denial of service or leak sensitive information. (CVE-2022-29181)