CVE-2026-56096: Apache Solr Information Disclosure Flaw

CVE-2026-56096 Overview

CVE-2026-56096 is a query injection vulnerability affecting a TYPO3 extension that forwards user-supplied search parameters to Apache Solr. The extension fails to restrict advanced Solr query syntax, including wildcards, field selectors, and range queries. A remote, unauthenticated attacker can craft queries that enumerate indexed field names and extract stored values. The extraction works through boolean-based and range-based blind techniques, independent of any site-specific configuration. The vulnerability is tracked under [CWE-943: Improper Neutralization of Special Elements in Data Query Logic] and is documented in the TYPO3 Security Advisory #2026-025.

Critical Impact
Unauthenticated attackers can extract confidential indexed data from Apache Solr through blind query injection, exposing information that was never intended to be searchable by the public.

Affected Products

TYPO3 CMS extension integrating with Apache Solr (see TYPO3 Security Advisory #2026-025)
Apache Solr backends receiving unfiltered queries through the affected extension
TYPO3 installations exposing the search endpoint to unauthenticated users

Discovery Timeline

2026-08-25 - CVE-2026-56096 published to NVD
2026-08-26 - Last updated in NVD database

Technical Details for CVE-2026-56096

Vulnerability Analysis

The affected TYPO3 extension accepts a search query parameter from HTTP requests and forwards it directly to Apache Solr. Solr supports a rich query language that includes wildcard expressions such as *, field-scoped searches using the field:value syntax, and inclusive or exclusive range queries expressed as [a TO b] or {a TO b}. When the extension does not neutralize these operators, the attacker controls how Solr interprets the search string.

An attacker submits crafted queries and observes whether the search returns results. Boolean-based extraction confirms whether a specific field value satisfies a predicate. Range-based extraction narrows a value using binary-search style comparisons. Repeated queries reconstruct sensitive values character by character or bucket by bucket. Because the attack targets the Solr index directly, no site-specific configuration is required for exploitation.

Root Cause

The root cause is missing input sanitization on the search parameter before it is concatenated into the Solr query string. The extension treats operator characters and field selectors as data rather than as control syntax. This is a classic query language injection weakness classified under [CWE-943].

Attack Vector

Exploitation occurs over the network against the public search endpoint. The attacker sends HTTP GET or POST requests containing Solr query operators in the search parameter. No authentication or user interaction is required. The attacker iterates through queries such as fieldname:[a TO m] to determine which range contains data, then narrows the range until individual values are recovered. Field discovery uses wildcard queries against schema metadata that Solr exposes when unrestricted syntax is permitted.

Refer to the TYPO3 Security Advisory #2026-025 for vendor-supplied exploitation constraints and technical details. No public proof-of-concept code has been published.

Detection Methods for CVE-2026-56096

Indicators of Compromise

Search query parameters containing Solr operators such as :, [, ], {, }, *, TO, or AND/OR submitted by unauthenticated clients
Bursts of near-identical search requests from a single source address that iterate over field names or value ranges
Web server logs showing search endpoints returning inconsistent result counts for structurally similar queries
Apache Solr access logs containing field-scoped queries that reference fields not exposed by the public search UI

Detection Strategies

Inspect application and web server logs for search parameters containing raw Solr query syntax and alert when operator density exceeds a baseline
Correlate high-frequency search requests with response-size or hit-count variations to identify blind extraction patterns
Deploy web application firewall rules that flag Solr reserved characters submitted through user-facing search endpoints

Monitoring Recommendations

Enable verbose logging on the Apache Solr select handler and forward logs to a centralized analytics platform
Track per-IP request rates against the TYPO3 search endpoint and alert on sustained enumeration behavior
Monitor for queries referencing internal field names, admin fields, or fields prefixed with underscores that indicate schema probing

How to Mitigate CVE-2026-56096

Immediate Actions Required

Apply the extension update referenced in the TYPO3 Security Advisory #2026-025 as soon as the vendor patch is available
Restrict the public search endpoint to authenticated users where feasible until patching is complete
Rate-limit search requests at the reverse proxy or WAF to slow blind extraction attempts

Patch Information

TYPO3 has published Security Advisory #2026-025 for this issue. Administrators should upgrade the affected extension to the fixed version identified in the advisory. Review the advisory for the exact version numbers and any post-upgrade configuration steps.

Workarounds

Sanitize the search input server-side to strip or escape Solr reserved characters including + - && || ! ( ) { } [ ] ^ " ~ * ? : \ /
Use the Solr edismax query parser with a fixed qf field list and disable raw Lucene syntax on the public handler
Configure Solr to expose only a minimal, non-sensitive field set to the search request handler used by the extension
Place a web application firewall in front of the TYPO3 site with rules that block Solr operator injection patterns

bash

# Example Solr requestHandler hardening in solrconfig.xml
# Restrict the public handler to edismax and a fixed field list
<requestHandler name="/select" class="solr.SearchHandler">
  <lst name="defaults">
    <str name="defType">edismax</str>
    <str name="qf">title content</str>
    <str name="fl">title,url,snippet</str>
    <str name="echoParams">none</str>
  </lst>
  <lst name="invariants">
    <str name="q.op">AND</str>
  </lst>
</requestHandler>