CVE-2025-61024: Virtuoso Open-Source DoS Vulnerability

CVE-2025-61024 Overview

CVE-2025-61024 affects the sqlo_try_in_loop component of OpenLink virtuoso-opensource version 7.2.11. Attackers can submit crafted SQL statements to trigger a Denial of Service (DoS) condition in the database server. The flaw is network-exploitable and requires no authentication or user interaction. The Common Weakness Enumeration classifies this issue under [CWE-89] (Improper Neutralization of Special Elements used in an SQL Command).

Critical Impact
Remote attackers can crash or render unresponsive Virtuoso database instances by submitting malformed SQL queries, disrupting any application or service that relies on the affected database.

Affected Products

OpenLink Virtuoso Open Source v7.2.11
Applications and services backed by affected Virtuoso instances
Network-exposed SPARQL and SQL endpoints served by Virtuoso

Discovery Timeline

2026-06-23 - CVE-2025-61024 published to NVD
2026-06-23 - Last updated in NVD database

Technical Details for CVE-2025-61024

Vulnerability Analysis

The vulnerability resides in the sqlo_try_in_loop routine of the Virtuoso SQL optimizer. The function processes SQL statements that contain IN predicates inside loop optimization paths. When the optimizer receives a specifically crafted statement, it fails to handle the input safely and the database process terminates or becomes unresponsive. The result is a Denial of Service that interrupts query processing for all connected clients.

Virtuoso commonly serves as a backend for Linked Data platforms, SPARQL endpoints, and enterprise data integration pipelines. An outage in this layer cascades to dependent applications. Because exploitation depends only on submitting a query, any user or anonymous client able to reach the SQL or SPARQL interface can trigger the condition.

Root Cause

The defect is an input handling failure within the query optimizer's loop processing logic. The sqlo_try_in_loop routine does not properly validate or sanitize the structure of crafted SQL constructs before evaluating them. Improper neutralization of SQL elements ([CWE-89]) inside the optimizer drives the process into an unrecoverable state, terminating availability for the affected instance.

Attack Vector

Exploitation occurs over the network through any interface that accepts SQL queries from clients. An attacker establishes a connection to a Virtuoso endpoint and submits the crafted statement. No credentials, prior compromise, or user interaction is required. The attack targets availability only — confidentiality and integrity are not affected based on the published CVSS metrics.

The vulnerability mechanism is documented in the upstream issue tracker. See the GitHub Issue Discussion for the original technical report and reproducer details.

Detection Methods for CVE-2025-61024

Indicators of Compromise

Unexpected termination or restart of the virtuoso-t server process
Abrupt loss of connectivity to SQL or SPARQL endpoints
Error logs referencing the sqlo_try_in_loop function or optimizer failures
Spikes in malformed or unusually structured IN clause queries from a single source

Detection Strategies

Monitor Virtuoso server logs for crash signatures, segmentation faults, or repeated process restarts
Inspect inbound SQL traffic for anomalous IN predicate patterns targeting the optimizer
Correlate database unavailability events with preceding query traffic from the same client IP

Monitoring Recommendations

Track process uptime and availability metrics for all Virtuoso instances
Alert on repeated client-initiated query failures followed by service downtime
Forward Virtuoso application logs to a centralized SIEM for correlation against network telemetry

How to Mitigate CVE-2025-61024

Immediate Actions Required

Restrict network access to Virtuoso SQL and SPARQL endpoints to trusted clients only
Place affected instances behind a reverse proxy or query filter that can reject malformed SQL
Require authentication on all interfaces and disable anonymous query access where possible
Monitor the upstream issue for patch availability

Patch Information

No official vendor patch is referenced in the NVD entry at time of publication. Track the upstream openlink/virtuoso-opensource repository and the linked GitHub issue for fix commits and updated release tags beyond version 7.2.11.

Workarounds

Apply network-level access controls (ACLs, firewall rules) to limit who can reach Virtuoso ports
Deploy a database proxy that validates query structure and blocks suspicious IN predicates
Implement query rate limiting and connection throttling per source address
Run Virtuoso under a service supervisor that auto-restarts the process on crash to limit downtime

bash

# Example: restrict Virtuoso default SQL port (1111) to a trusted management subnet
iptables -A INPUT -p tcp --dport 1111 -s 10.0.0.0/24 -j ACCEPT
iptables -A INPUT -p tcp --dport 1111 -j DROP

# Example: restart policy via systemd unit override
# /etc/systemd/system/virtuoso.service.d/override.conf
[Service]
Restart=on-failure
RestartSec=5s