dbcve.org
SolrApplication · Apache

CVE-2021-44548

CRITICAL · 9.8 CVSS v3.1 Published 2021-12-23
Fix available
A fix is available. Upgrade to 8.11.1 or later.
See remediation →
100/100
Remediation priority · Urgent
Remotely reachable No privileges Zero-click

Official description Straight from the sourceThe vendor's or NVD's own wording, published unedited. Authoritative, but often terse — it says what broke, rarely what to do.

NVD · unedited
An Improper Input Validation vulnerability in DataImportHandler of Apache Solr allows an attacker to provide a Windows UNC path resulting in an SMB network call being made from the Solr host to another host on the network. If the attacker has wider access to the network, this may lead to SMB attacks, which may result in: * The exfiltration of sensitive data such as OS user hashes (NTLM/LM hashes), * In case of misconfigured systems, SMB Relay Attacks which can lead to user impersonation on SMB Shares or, in a worse-case scenario, Remote Code Execution This issue affects all Apache Solr versions prior to 8.11.1. This issue only affects Windows.

Technical summary Written by usOur analysis, written from the advisory, the CVSS vector and the affected-version data. It adds context the advisory leaves out, and never invents facts that are not in the source.

dbcve analysis · high confidence

Improper input validation in Apache Solr's DataImportHandler allows attackers to supply Windows UNC paths, triggering outbound SMB connections from the Solr server. This enables NTLM/LM hash exfiltration and potentially SMB Relay attacks leading to user impersonation or RCE. The vulnerability is Windows-specific and affects all Solr versions prior to 8.11.1.

MitigationUpgrade Apache Solr to version 8.11.1 or later. Until patched, consider disabling or restricting DataImportHandler and blocking outbound SMB traffic at the network perimeter.

Verify against the referenced sources before acting — the references below are authoritative for this CVE, this summary is not.

Affected products & versions What the vendor confirmedThe version ranges the vendor confirmed as vulnerable. If your version sits inside a range here, treat yourself as exposed until you have upgraded.

NVD · CPE data
SolrApplication
Affected:< 8.11.1

CVSS breakdown How the score is builtThe industry scoring standard. It rates how the flaw is reached, what it takes to exploit, and what an attacker gains — the score is derived from those, not the other way round.

From the vector
Attack vector
Network
Complexity
Low
Privileges
None
User interaction
None
Scope
Unchanged
Confidentiality
High
Integrity
High
Availability
High

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H

Am I affected? How to checkSteps we derive from the advisory and the affected-version data, so you can decide whether this CVE reaches your setup. They are a guide, not a scan — your own configuration is the authority.

dbcve checks

Work through these to decide whether this CVE applies to you.

  1. Verify Solr runs on Windows
    Check the operating system where Solr is installed (e.g., run 'systeminfo' on Windows or check process environment). This vulnerability only affects Windows deployments.
    Affected if The Solr server is running on a Windows host.
  2. Confirm Solr version
    Check the installed Solr version. On Windows, this is often visible in the Solr service name, or check the solr -version command output, or inspect the VERSION.txt file in the Solr installation directory.
    Affected if The installed version is any version of Apache Solr prior to 8.11.1 (e.g., 8.11.0, 8.10.x, 8.x, 7.x, 6.x, etc.).
  3. Verify DataImportHandler is enabled
    Check if the DataImportHandler (dataimport) module is loaded. Look for 'dataimport' in the Solr configuration (solrconfig.xml) or check for /solr/admin/dataimport endpoints being accessible. Also check if lib tags in solrconfig.xml include dataimporthandler jars.
    Affected if DataImportHandler is enabled and accessible, meaning the dataimport request handler is configured in solrconfig.xml.
  4. Confirm dataimport endpoint is exposed
    Attempt to access the dataimport handler endpoint (e.g., curl http://localhost:8983/solr/<core>/dataimport or check Solr Admin UI for DataImport tab). Verify the handler responds without authentication if unsecured.
    Affected if The dataimport endpoint is reachable over network without proper restrictions.

A user is affected if they are running Apache Solr on Windows with DataImportHandler enabled and the installed version is prior to 8.11.1, allowing an attacker to supply Windows UNC paths to trigger outbound SMB connections.

Generated from the published advisory. Verify against your own configuration.

Check your environment

Paste your version and any relevant configuration and it will be compared against the affected criteria above. Do not include secrets or credentials.

AI-assisted, checked against the advisory. Informational, not a guarantee.

Remediation Closing itWhat it takes to close this. Where a vendor fix exists we point at it; where none exists we say so plainly, and can build one. Effort estimates are scoped from the advisory, not from your codebase.

dbcve · scoped
Upgrade available Upgrade to 8.11.1 or later
Fixed in 8.11.1
Interim mitigation

Upgrade Apache Solr to version 8.11.1 or later. Until patched, consider disabling or restricting DataImportHandler and blocking outbound SMB traffic at the network perimeter.

Recommended fix High confidence

Apache Solr 8.11.1 or later

  1. 1. Backup your current Solr configuration and data directories
  2. 2. Download Apache Solr 8.11.1 or later from the official Apache Solr website (solr.apache.org)
  3. 3. Stop the currently running Solr service
  4. 4. Install the new Solr version (8.11.1 or later) using the standard installation process for your environment
  5. 5. Restore your Solr configuration to the new installation
  6. 6. Start the Solr service
  7. 7. Verify that Solr is running correctly and DataImportHandler is functional
  8. 8. Confirm the Solr version is 8.11.1 or later by checking the admin UI or running: bin/solr version
Caveat Review Solr 8.11.x release notes for any breaking changes from your current version before upgrading

Generated from the published advisory — verify against the referenced sources before acting.

Fix this in Solr Scoped from the published advisory
  • Consultation3.0 h
  • Implementation4.0 h
  • Testing6.0 h
  • Review / QA3.0 h
16.0 hours of engineering $2,760
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References Go to the primary sourcePrimary sources — vendor advisories, patches and trackers. Where our summary and a reference disagree, the reference wins.

Primary sources

Practitioner notes

Contributed

Peer-ranked notes from engineers who’ve handled CVE-2021-44548 in production — separate from our analysis above.

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What this is

A place for practitioners to share what actually worked: a mitigation you’ve tested, a configuration change, a version- or environment-specific caveat, or a link to a verified patch. The most useful notes rise to the top as peers upvote them, so the signal stays high.

What belongs here
  • Verified mitigations, workarounds, and config changes
  • Version or environment caveats, and links to real fixes
  • No weaponised exploit code, or anything meant to cause harm
  • No spam, self-promotion, credentials, or personal data