CVE-2021-44548: Apache Solr Improper Input Validation Vulnerability

solr Updated 02 Oct 2025

Summary

06/03/2024

Disclosed on

CVE-2021-44548

CVE

Yes i

Fix available

Critical

Severity

Not published

CVSS Score

CVE-2021-44548: Apache Solr information disclosure vulnerability through DataImportHandler. Affects solr versions < 8.11.1. Fixed in 8.11.1. How to fix ↓

Also tracked for

org.apache.solr:solr-parent · Maven

The same CVE-2021-44548 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, hit highlighting, faceted search, and many other features. Solr is widely used in various applications for efficient and scalable search functionality. However, a vulnerability has been discovered in the DataImportHandler component of Apache Solr, which allows an attacker to provide a Windows UNC path, leading to an SMB network call from the Solr host to another host on the network. This vulnerability affects all Apache Solr versions prior to 8.11.1 and only impacts Windows systems.

Vulnerability Detail

The vulnerability arises due to improper input validation in the DataImportHandler of Apache Solr. By providing a Windows UNC path, an attacker can trigger an SMB network call from the Solr host to another host on the network. If the attacker has broader access to the network, this can result in various SMB attacks, including the exfiltration of sensitive data such as OS user hashes (NTLM/LM hashes). In misconfigured systems, it can also lead to SMB Relay Attacks, potentially allowing user impersonation on SMB Shares or even remote code execution. This vulnerability poses a critical risk to affected systems.

How To Fix

Minimum fixed version

8.11.1

This is the first release that contains the fix.

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Workaround

There is no known workaround for this vulnerability. It is essential to apply the official patch by upgrading to Apache Solr 8.11.1 or later.

Conclusion

The Apache Solr Improper Input Validation vulnerability (CVE-2021-44548) poses a critical risk to Windows systems running affected versions of Apache Solr. It allows an attacker to trigger SMB network calls, potentially leading to data exfiltration, user impersonation, or even remote code execution. It is highly recommended to upgrade to Apache Solr 8.11.1 or later to mitigate this vulnerability. For further support on vulnerability remediation, please contact DevNack.com.

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