Actively exploited in the wild
Apache Solr VelocityResponseWriter Plug-In Remote Code Execution Vulnerability
Apache - Solr · Listed in the CISA KEV since 2021-11-03. This indicates confirmed attacks in production environments.
Required action: Apply updates per vendor instructions.
CVE-2019-17558
HighCVSS 7.5KEVSummary
Apache Solr 5.0.0 to Apache Solr 8.3.1 are vulnerable to a Remote Code Execution through the VelocityResponseWriter. A Velocity template can be provided through Velocity templates in a configset `velocity/` directory or as a parameter. Parameter-provided templates are disabled by default but can be enabled by setting `params.resource.loader.enabled` to `true`, which requires configuration API access. Solr 8.4 removed the params resource loader entirely and only enables configset-provided template rendering when the configset is `trusted`.
Risk Assessment
An attacker with access to the configuration API could achieve remote code execution on the Solr server, potentially leading to full system compromise and data leakage. The risk is high because Solr often processes data indexed from various sources.
Recommendation
Update Apache Solr to version 8.4 or later, where the params resource loader was removed. If updating is not possible, restrict access to the configuration API and ensure `params.resource.loader.enabled` remains disabled.
Other vulnerabilities in Apache Solr
See all- CVE-2026-22444High
The "create core" API of Apache Solr 8.6 through 9.10.0 lacks sufficient input validation on some API parameters, which can cause Solr to check the existence of and attempt to read file-system paths that should be disallowed by Solr's "allowPaths" security setting. These read-only accesses can allow users to create cores using unexpected configsets if any are accessible via the filesystem. On Windows systems configured to allow UNC paths this can additionally cause disclosure of NTLM "user" hashes.
- CVE-2026-22022High
Deployments of Apache Solr 5.3.0 through 9.10.0 that rely on Solr's "Rule Based Authorization Plugin" are vulnerable to allowing unauthorized access to certain Solr APIs, due to insufficiently strict input validation in those components. Only deployments that meet all of the following criteria are impacted: use of the RuleBasedAuthorizationPlugin, a config with multiple roles, a permission list using one or more of the predefined permission rules (config-read, config-edit, schema-read, metrics-read, security-read), no "all" permission defined, and a networking setup that allows unfiltered requests to Solr.
- CVE-2017-3163High
A vulnerability in Apache Solr allows attackers to exploit the index replication feature to read files from the server due to improper validation of file names. Versions before 5.5.4 and 6.x before 6.4.1 are susceptible to path traversal attacks.
- CVE-2017-7660High
Apache Solr uses a PKI based mechanism to secure inter-node communication when security is enabled. It is possible to create a specially crafted node name that does not exist as part of the cluster and point it to a malicious node, which can trick other nodes in the cluster.
- CVE-2019-0193HighActively exploited
In Apache Solr, the DataImportHandler (DIH) has a feature where the entire DIH configuration can come from a request's 'dataConfig' parameter. The debug mode of the DIH admin screen uses this, which is a security risk since a DIH config can contain scripts. Starting with Solr 8.2.0, use of this parameter requires setting the Java System property 'enable.dih.dataConfigParam' to true.
- CVE-2017-12629Critical
Apache Solr before 7.1 is vulnerable to remote code execution, which can be exploited via an XXE attack in conjunction with the Config API add-listener command, leading to the RunExecutableListener class.
- CVE-2026-44825High
Apache Solr versions 9.4.0 through 9.10.1 and 10.0.0 contain hardcoded default credentials in the Basic Authentication setup tool (bin/solr auth enable). A remote attacker can gain full administrative access to the cluster using publicly known default passwords.
Original NVD description (English source)
Apache Solr 5.0.0 to Apache Solr 8.3.1 are vulnerable to a Remote Code Execution through the VelocityResponseWriter. A Velocity template can be provided through Velocity templates in a configset `velocity/` directory or as a parameter. A user defined configset could contain renderable, potentially malicious, templates. Parameter provided templates are disabled by default, but can be enabled by setting `params.resource.loader.enabled` by defining a response writer with that setting set to `true`. Defining a response writer requires configuration API access. Solr 8.4 removed the params resource loader entirely, and only enables the configset-provided template rendering when the configset is `trusted` (has been uploaded by an authenticated user).