---
id: "CVE-2019-17558"
kind: "vulnerability"
aliases: ["CVE-2019-17558"]
title: "Apache Solr: Apache Solr VelocityResponseWriter Plug-In Remote Code Execution Vulnerability"
severity: "critical"
cvss: 7.5
epss: 0.98567
exploited: true
status: "open"
category: "package"
products: [{"name": "Apache Solr", "fixed": [], "affected": "", "ecosystem": "vendor"}]
ecosystems: ["vendor"]
tags: ["exploited", "java", "package", "self-hosted", "solr"]
not_affected_if: ["no-solr-deployed", "velocity-writer-disabled"]
published_at: "2019-12-30T17:15:19+00:00"
first_seen_at: "2026-10-23T19:11:53+00:00"
updated_at: "2026-10-23T21:57:35+00:00"
sources: [{"source": "kev", "url": "https://www.cisa.gov/known-exploited-vulnerabilities-catalog?search_api_fulltext=CVE-2019-17558", "first_seen_at": "2026-10-23T19:11:53+00:00"}, {"source": "epss", "url": "https://api.first.org/data/v1/epss?cve=CVE-2019-17558", "first_seen_at": "2026-10-23T19:13:44+00:00"}, {"source": "nvd", "url": "https://nvd.nist.gov/vuln/detail/CVE-2019-17558", "first_seen_at": "2026-10-23T21:57:35+00:00"}]
---

# Apache Solr: Apache Solr VelocityResponseWriter Plug-In Remote Code Execution Vulnerability

Apache Solr's VelocityResponseWriter plug-in has a flaw that allows remote code execution on the server. An attacker can run commands on a Solr host without logging in, and CISA lists it as actively exploited.

_Summary, check and fix written by a model from the sources; labelled as such._

## Affected

- vendor:Apache Solr affected ? fixed ?

## Fix

Apply the vendor update per Apache Solr instructions; the affected and fixed versions are not stated in the sources.
If you cannot patch, check the Solr configuration for the VelocityResponseWriter (velocity) response writer and disable it if unused.

## Timeline

- 2026-10-23T19:11:53+00:00 kev https://www.cisa.gov/known-exploited-vulnerabilities-catalog?search_api_fulltext=CVE-2019-17558
- 2026-10-23T19:13:44+00:00 epss https://api.first.org/data/v1/epss?cve=CVE-2019-17558
- 2026-10-23T21:57:35+00:00 nvd https://nvd.nist.gov/vuln/detail/CVE-2019-17558

## From the sources

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).

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