CVE-2019-0193 is a dataimporthandler code injection vulnerability in Apache Solr. CISA added it to the Known Exploited Vulnerabilities catalogue on 10 December 2021, which means attackers have used it in real attacks. The optional Apache Solr module DataImportHandler contains a code injection vulnerability.
What the vulnerability means in Apache Solr
CVE-2019-0193 affects the optional Apache Solr DataImportHandler module, so the security issue is not just “a bug in Solr”, but a code injection path in a feature that can execute attacker-controlled input as logic. That makes the vulnerability dangerous anywhere the module is enabled and exposed to untrusted requests.
Code injection matters because it can turn a search or indexing component into an execution foothold. In practice, the risk is shaped by how Solr is deployed, whether the module is enabled, and whether attacker reachability extends to the relevant endpoint.
Why code injection is dangerous in a search platform
Search infrastructure often sits close to content pipelines, internal datasets, and operational data stores. When a module can interpret attacker input as code, the blast radius can extend beyond search results into data access, server-side execution, and wider application trust boundaries.
That is why this class of issue is treated as more than a simple input-validation failure. A code injection flaw can let an attacker move from ordinary request handling into unintended server behavior, which is especially serious in platforms that are embedded in larger web and data architectures.
How organisations assess exposure and likely impact
Exposure review starts with inventory: identify where Apache Solr is deployed, whether DataImportHandler is enabled, and whether any instance is reachable from untrusted networks or public-facing applications. Vendor advisories and the NIST National Vulnerability Database remain the authoritative places to confirm affected product context and remediation guidance.
For a vulnerability already added to the CISA KEV catalogue, prioritisation should assume real-world exploitation is plausible, not merely theoretical. Organisations should also review application logs, reverse proxies, WAF telemetry, and host activity for unexpected requests to Solr endpoints or follow-on behaviour consistent with server-side compromise.
Remediation, detection, and post-incident review
Remediation should follow the vendor’s fix guidance for the exact Solr deployment, but until patching is complete, the safest compensating controls are to disable the vulnerable module if it is not required, restrict access to trusted networks, and reduce the attack surface around the Solr service. General vulnerability handling principles are also captured in the Vulnerability Management Guide.
Detection should focus on suspicious request patterns, unexpected process execution, and any change to data sources or configuration after exploitation. If compromise is suspected, review adjacent systems that may have trusted the Solr host, because a code injection path can become a springboard into credentials, service accounts, data connectors, or other internal resources.
Risk and Threat Considerations
This kind of flaw is dangerous because it combines remote reachability with code execution potential, and CISA KEV inclusion indicates attackers have already used it in the wild. That makes delayed remediation a live exposure issue, not just a patch-management backlog item.
Failure mechanism: A malicious request reaches the vulnerable DataImportHandler path, injects code, and causes Solr to execute attacker-controlled behaviour on the server.
Impact: The attacker may gain server-side execution, alter or extract data, and use the compromised service as an entry point for deeper internal compromise.
Standards & Framework Alignment
This section maps relevant standards and security frameworks to the operational risks and controls described in this guidance.
MITRE ATT&CK addresses the attack and risk surface, while NIST SP 800-53 Rev 5 and CIS Controls v8 set the governance and control requirements practitioners need to meet.
| Framework | Control / Reference | Relevance |
|---|---|---|
| NIST SP 800-53 Rev 5 | SI-10 — Information Input Validation | Code injection is driven by unsafe handling of request input. |
| AU-6 — Audit Record Review, Analysis, and Reporting | Detection and compromise review depend on reviewing logs and abnormal activity. | |
| CM-7 — Least Functionality | The vulnerable module should be removed or disabled when not required. | |
| Recommendation — Validate all Solr-facing inputs before they reach executable request paths. Review Solr logs and related telemetry for suspicious request patterns and post-exploit activity. Disable unused Solr modules and services to reduce the exposed attack surface. | ||
| CIS Controls v8 | CIS-7 — Continuous Vulnerability Management | The issue requires discovery, prioritisation, and remediation as an exploited vulnerability. |
| Recommendation — Prioritise and remediate the affected Solr deployment as an exploited vulnerability. | ||
| MITRE ATT&CK | T1190 — Exploit Public-Facing Application | The vulnerability is exploited through a reachable application endpoint. |
| Recommendation — Map exposed Solr endpoints to T1190 and hunt for exploitation attempts. | ||
Practitioner Guidance
Why practitioners should care: Treat any enabled, reachable instance of the vulnerable Solr module as an urgent exposure until it is patched or removed from service. The key judgement is not whether Solr is “important”, but whether the affected feature is operationally necessary and still exposed to untrusted traffic.
What to watch for: Prioritise assets by internet exposure, business criticality, and whether the module is actually in use. If the feature is unnecessary, removing it is often safer than leaving a dormant attack surface in place.