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Solr Security

The authoritative guide on implementing security is in the Solr Reference Guide. This page describes security features in general, but also provides information about CVEs that have been patched or dependencies which do not require a patch for Solr.

Security Announcements

If you believe you have discovered a vulnerability in Lucene or Solr, please follow these ASF guidelines for reporting it.

Current state of affairs

  • SSL support was added in version 4.2 (SolrCloud v4.7).
  • Protection of Zookeeper content through ACLs was added in version 5.0
  • Authentication and Authorization plugin support was added in 5.2 (SolrCloud only).
    • Several bugs in this support were fixed in 5.3, so it's strongly recommended to use 5.3 or later if this feature is desired. The general recommendation is to always use the latest released version.
  • Basic Auth & Kerberos plugins and Rule-based Authorization plugin was added in 5.3

There is (as of 5.3) no role-based restrictions on the Admin UI, so be aware that anyone with access to Admin UI will be able to do anything with your system.

Need for firewall

Even though you add SSL or Authentication plugins, it is still strongly recommended that the application server containing Solr be firewalled such the only clients with access to Solr are your own. A default/example installation of Solr allows any client with access to it to add, update, and delete documents (and of course search/read too), including access to the Solr configuration and schema files and the administrative user interface.

If there is a need to provide query access to a Solr server from the open internet, it is highly recommended to use a proxy, such as one of these.

Cross-Site Scripting (XSS)

Solr has no known cross-site scripting vulnerabilities.

Quick XSS tip:

Problem: What if you want the browser to highlight text, but you also want to protect yourself from XSS and escape the HTML output? Solution: One solution is to escape the HTML output and then reapply the em tags. Now the rest of the snippet is safe and the browser will recognize the highlighted text.

For example, with groovy/grails you could have the following in your controller:

snippet = snippet.encodeAsHTML()
snippet = snippet.replaceAll('&lt;em&gt;', '<em>')
snippet = snippet.replaceAll('&lt;/em&gt;', </em>)

Cross-Site Request Forgery (CSRF)

Even if a Solr instance is protected by good firewalls so that "bad guys" have no direct access, that instance may be at risk to potential "Cross-Site Request Forgery" based attacks if the following are all true:

  1. Some number of "good guys" have direct access to that Solr instance from their web browsers.
  2. A "bad guy" knows/guesses the host:port/path of the Solr instance (even though they can not access it directly)
  3. The bad guy can trick one of the good guy into clicking a maliciously crafted URL, or loading a webpage that contains malicious javascript.

This is because Solr's most basic behavior is to receive updates and deletes via HTTP. If you have a firewall or other security measure restricting Solr's /update handler so it only accepts connections from approved hosts/clients, but you are approved then you could inadvertently be tricked into loading a web page that initiates an HTTP Connection to Solr on your behalf.

It's important to keep this in mind when thinking about what it means to "secure" an instance of Solr (if you have not already).

A basic technique that can be used to mitigate the risk of a possible CSRF attack like this is to configure your Servlet Container so that access to paths which can modify the index (ie: /update, /update/csv, etc...) are restricted either to specific client IPs, or using HTTP Authentication.

Document Level Security

Manifold CF (Connector Framework)

One way to add document level security to your search is through Apache ManifoldCF. ManifoldCF "defines a security model for target repositories that permits them to enforce source-repository security policies".

It works by adding security tokens from the source repositories as metadata on the indexed documents. Then, at query time, a Search Component adds a filter to all queries, matching only documents the logged-in user is allowed to see. ManifoldCF supports AD security out of the box.

Write Your Own RequestHandler or SearchComponent

*Stub - this is incomplete*

If ManifoldCF does not solve your need, first consider writing a ManifoldCF plugin. Or roll your own.

If you need permission based authentication – where user A can update document 1 and 2, but not 3 – you will need to augment the request with user information. Either you can add parameters to the query string (?u=XXX&p=YYY) or use a custom dispatcher filter that augments the context:

public class CustomDispatchFilter extends SolrDispatchFilter
  protected void execute( HttpServletRequest req, SolrRequestHandler handler, SolrQueryRequest sreq, SolrQueryResponse rsp)
    // perhaps the whole request
    sreq.getContext().put( "HttpServletRequest", req );

    // or maybe just the user
    sreq.getContext().put( "user", req.getRemoteUser());

    core.execute( handler, sreq, rsp );

public class AuthenticatingHandler extends RequestHandlerBase
  public void handleRequestBody(SolrQueryRequest req, SolrQueryResponse rsp) throws Exception {

    HttpServletRequest httpreq = (HttpServletRequest)
      req.getContext().get( "HttpServletRequest" );

    if( httpreq.isUserInRole( "editor" ) ) {

    String user = (String)req.getContext().get( "user" );

Streaming Consideration

If streaming is enabled, you need to make sure Solr is as secure as it needs to be. When streaming is enabled, the parameters "stream.url" will go to a remote site and download the content. Likewise, "stream.file" will read a file on disk.

Streaming is disabled by default and is configured from solrconfig.xml

  <requestParsers enableRemoteStreaming="false" ... />

Indirect compromise through Tika vulnerabilities

One of the contrib modules that Solr includes is called SolrCell. This module adds the Extracting Request Handler. This component utilizes Apache Tika to parse rich documents like PDF and Microsoft Office and index the document contents into Solr.

The Tika software has had some security vulnerabilities. It would be theoretically possible for an attacker to upload a specially crafted file to be processed by Tika running inside Solr, or to trick an administrator into uploading such a file, and in that way compromise the Solr install.

For reasons not related to security, it is strongly recommended that this contrib module is never used in production. Tika can crash, and if such a crash happens in the SolrCell module, Solr will crash too. If that advice is followed, it would be very difficult to utilize Tika vulnerabilities to compromise Solr.

Solr and Vulnerability Scanning Tools

Many organizations have policies where software to be installed on the network must pass an examination by a vulnerability scanner which attempts to determine if there are known vulnerabilities in the application.

Solr includes many dependencies which may trigger warnings from a vulnerability scan but which the Lucene/Solr community has determined that they are false positives. As a general rule, the Lucene PMC will not accept the output of a vulnerability scan as a security report.

The following table lists the dependencies and associated CVEs which are not considered problems for Lucene or Solr.

Solr Versions

Jar or Path

Related CVEs

Date Added

Status & Notes


tika-core.1.17.jar (and earlier)


6 Jun 2018

Solr does not run tika-server, so this is not a problem.


tika-core.1.17.jar (and earlier)

2018-1338, 2018-1339

6 Jun 2018

These issues would only be exploitable if untrusted files are indexed with SolrCell. This is not recommended in production systems as indicated above. Additionally, Solr upgraded to Tika 1.18 in Solr 7.4.


jackson-databind-2.5.4.jar (and earlier)

2017-15095, 2017-17485, 2017-7525, 2018-5968, 2018-7489

6 Jun 2018

Jackson was upgraded to 2.9.5 in Solr 7.4.



2014-7940, 2016-6293, 2016-7415, 2017-14952, 2017-17484, 2017-7867, 2017-7868

6 Jun 2018

All of these issues apply to the C++ release of ICU and not ICU4J, which is what Lucene uses.


icu4j-56.1.jar, icu4j-59.1.jar


6 Jun 2018

Issue applies only to the C++ release of ICU and not ICU4J, which is what Lucene uses. ICU4J is at v63.2 as of Lucene/Solr 7.6.0


hadoop-auth-2.7.4.jar, hadoop-hdfs-2.7.4.jar (all Hadoop)


6 Jun 2018

Does not impact Solr because Solr uses Hadoop as a client library.




6 Jun 2018

This is only used at compile time and it cannot be used to attack Solr. Since it is generally unnecessary, the dependency has been removed as of 7.5.0.

5.5.5, 6.2.0-today


2016-6809, 2018-1335, 2018-1338, 2018-1339

6 Jun 2018


; reported CVEs are not related to OggVorbis at all.




6 Jun 2018

Only used in Lucene Benchmarks and Solr tests.


velocity-tools-2.0.jar contains Apache Struts 2.0.0

link to CVEs

3 Nov 2018

Solr does not ship a Struts jar. This is a transitive POM listing and not included with Solr (see comment in SOLR-2849).




3 Nov 2018

Dependency for Hadoop and Calcite. ??



3 Nov 2018

Used only in DataImportHandler tests and example implementation, which should not be used in production.




31 Dec 2018

JUnit only used in tests; CVE only refers to a Jenkins plugin not used by Solr.




31 Dec 2018

Only used in Solr tests.



2017-14868, 2017-14949

31 Dec 2018

Solr should not be exposed outside a firewall where bad actors can send HTTP requests.


commons-compress (only as part of Ant 1.8.2)

2012-2098, 2018-1324, 2018-11771

31 Dec 2018

Only used in test framework and at build time.




31 Dec 2018

Only used with the Carrot2 clustering engine.




31 Dec 2018





3 Jan 2019

Dependency of Carrot2 and used during compilation, not at runtime (see SOLR-769).


slf4j-api-1.7.24.jar, jcl-over-slf4j-1.7.24.jar, jul-to-slf4j-1.7.24.jar


6 Feb 2019

The reported CVE impacts org.slf4j.ext.EventData, which is not used in Solr.

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