CVE-2018-8026: Apache Solr XML External Entity Expansion (XXE) Vulnerability
Summary
CVE-2018-8026: XML external entity expansion in org.apache.solr:solr-core. Affects org.apache.solr:solr-core across 2 version ranges.
>= 6.0.0, < 6.6.5
>= 7.0.0, < 7.4.0
Fixed in 6.6.5 or 7.4.0, depending on the release line you run. How to fix ↓
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Background
Apache Solr is an open-source search platform built on Apache Lucene. It provides full-text search, hit highlighting, faceted search, real-time indexing, and more. Solr config files, such as currency.xml, enumsConfig.xml, and TIKA parsecontext config file, are used to configure various aspects of Solr's functionality. These config files can be manipulated to exploit an XML external entity expansion (XXE) vulnerability in Solr versions 6.0.0 to 6.6.4 and 7.0.0 to 7.3.1. The vulnerability allows an attacker to read arbitrary local files from the Solr server or the internal network by using file/ftp/http protocols. The manipulated files can be uploaded as configsets using Solr's API, providing an avenue for exploitation.
Vulnerability Detail
The XML external entity expansion (XXE) vulnerability in Apache Solr allows an attacker to read arbitrary local files from the Solr server or the internal network. This vulnerability affects Solr versions 6.0.0 to 6.6.4 and 7.0.0 to 7.3.1. The vulnerability is present in Solr config files, such as currency.xml, enumsConfig.xml, and TIKA parsecontext config file. These files can be manipulated to include external entities or exploit the Xinclude functionality. By using file/ftp/http protocols, an attacker can retrieve sensitive information from the server or internal network. This can lead to unauthorized access, data leakage, and potential compromise of the Solr server.
How To Fix
Latest published version: 10.0.0 as of 23 Oct 2026
Upgrading to it may include breaking changes; the versions below are the minimum fixed release for this vulnerability.
If you can't move to the latest
The minimum fixed version depends on the release line you run.
-
>= 6.0.0, < 6.6.56.6.5 -
>= 7.0.0, < 7.4.07.4.0
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Workaround
As a temporary workaround, it is possible to disable the Xinclude functionality in Solr config files. This can be done by removing or commenting out the Xinclude-related configurations in currency.xml, enumsConfig.xml, and TIKA parsecontext config file. However, this workaround may impact certain functionalities that rely on Xinclude. It is recommended to apply the official patches or upgrade to the latest version as soon as possible.
Conclusion
The XML external entity expansion (XXE) vulnerability in Apache Solr can be exploited to read arbitrary local files from the server or internal network. It is crucial to upgrade to the latest patched version or apply the official patches to mitigate this vulnerability. Regularly updating Solr to the latest stable release is recommended to ensure the latest security fixes are applied. For further support on vulnerability remediation, please contact DevNack.com.
See every vulnerability recorded for org.apache.solr:solr-core →
FAQ
Apache Solr is an open-source search platform built on Apache Lucene. It provides full-text search, hit highlighting, faceted search, real-time indexing, and more.
This vulnerability affects Apache Solr versions 6.0.0 to 6.6.4 and 7.0.0 to 7.3.1.
An attacker can exploit this vulnerability by manipulating Solr config files to include external entities or exploit the Xinclude functionality. By using file/ftp/http protocols, the attacker can read arbitrary local files from the Solr server or the internal network.
This vulnerability can lead to unauthorized access, data leakage, and potential compromise of the Solr server. An attacker can retrieve sensitive information from the server or internal network.
To fix this vulnerability, it is recommended to upgrade to Apache Solr version 7.4.0 or later for versions 7.x.x, and version 6.6.5 or later for versions 6.x.x. Regularly updating Solr to the latest stable release is important to ensure the latest security fixes are applied.
References
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