CVE-2021-27905: Apache Solr SSRF Vulnerability
Summary
CVE-2021-27905: SSRF vulnerability with the Replication handler. Affects solr versions < 8.8.2. Fixed in 8.8.2. How to fix ↓
Also tracked for
- org.apache.solr:solr-parent · Maven
- lucene-solr · Debian:11
The same CVE-2021-27905 is tracked separately for each ecosystem and vendor. Its fix information is the same; the package and affected versions differ.
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Background
Apache Solr is an open-source search platform built on Apache Lucene. It provides full-text search, faceted search, and indexing capabilities. The ReplicationHandler in Apache Solr allows replication of index data from one Solr core to another. The 'masterUrl' parameter is used to designate another ReplicationHandler on a different Solr core for replication. However, prior to version 8.8.2, Solr did not properly validate this parameter, leading to a Server-Side Request Forgery (SSRF) vulnerability.
Vulnerability Detail
The SSRF vulnerability in Apache Solr allows an attacker to make arbitrary HTTP requests from the affected server, potentially accessing internal resources or performing actions on behalf of the server. This can lead to unauthorized data exposure, remote code execution, or other malicious activities. The vulnerability affects all versions of Solr prior to 8.8.2.
How To Fix
Minimum fixed version
8.8.2
This is the first release that contains the fix.
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Workaround
If upgrading to the latest version is not immediately feasible, a temporary workaround is to manually validate the 'masterUrl' parameter against a similar configuration used for the 'shards' parameter. This can be done by implementing custom validation logic in the application code that handles the ReplicationHandler. Here is an example in Java:
String masterUrl = request.getParameter("masterUrl");
String shards = request.getParameter("shards");
if (masterUrl != null && shards != null && masterUrl.startsWith("http://") && shards.startsWith("http://")) {
// Proceed with replication
} else {
// Handle invalid input
}
Conclusion
The SSRF vulnerability in Apache Solr can be mitigated by upgrading to version 8.8.2 or later. In the meantime, a temporary workaround is available by implementing custom validation for the 'masterUrl' parameter. It is important to take immediate action to protect the affected Solr installations from potential exploitation. For further assistance or information, please reach out to DevNack.com.
See every vulnerability recorded for solr →
FAQ
The vulnerability allows an attacker to make arbitrary HTTP requests from the affected server, potentially accessing internal resources or performing actions on behalf of the server. This can lead to unauthorized data exposure, remote code execution, or other malicious activities.
All versions of Apache Solr prior to 8.8.2 are affected by this vulnerability.
Yes, a temporary workaround is to manually validate the 'masterUrl' parameter against a similar configuration used for the 'shards' parameter. Custom validation logic can be implemented in the application code that handles the ReplicationHandler.
To upgrade to the fixed version (8.8.2 or later), refer to the upgrade instructions provided in the Solr documentation.
For further support or to report any additional issues, please contact info@devnack.com.
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