External risk intelligence

Apache Hive SSRF via Avro Schema Resolution

CVE advisorySeverity: CRITICAL (CVSS 9.1)

CVE-2026-55976

The vulnerability requires valid authentication, specific CREATE TABLE privileges, and network access to HiveServer2, which is typically situated within internal data analytics environments. While network-reachable, Hive is rarely exposed directly to the public internet, and the requirement for authenticated DDL privileges makes it an unlikely target for public-facing exploitation.

Server-Side Request Forgery

Halo Surface Signal: 2 out of 5 — less likely to be public-facing.

External exposure likelihood

Horizon Alert

Summary of the vulnerability and why it matters

A security vulnerability in Apache Hive allows authenticated users with table creation privileges to trick the system into accessing external or internal network resources. This could potentially expose sensitive information, such as cloud instance metadata or local server files, to the process running Hive. The main concern is confirming the relevance and exposure of this issue within your environment.

Attackers can make Hive access unauthorized URLs.
Matters if sensitive data is on cloud or internal networks.
Assess Hive's exposure to internal resources.

Attack Path

How an attacker could exploit the issue

An attacker with authenticated access and the ability to create tables can trick a Hive server into accessing a specified URL. This occurs when the server resolves the schema for an Avro table, potentially revealing sensitive internal information or resources.

Requires authenticated network access.
Triggered by resolving Avro schema URL.
Can expose internal services or files.

Live Threat

Current exploitation, exposure, and threat context

An authenticated remote attacker with table creation privileges could cause the Hive server to retrieve content from a URL they control. When this occurs, the Hive server process could be tricked into accessing sensitive information, such as cloud instance metadata, internal network resources, or local files on the server. This could happen when an attacker sets a malicious `avro.schema.url` property on an Avro table and another user subsequently queries it.

Server credentials and internal network details.
Authenticated user can set malicious URL property.
Exposure of sensitive server or cloud information.

Operational Fix

Recommended remediation, mitigation, and detection steps

This Server-Side Request Forgery vulnerability necessitates action from teams managing Apache Hive and its associated data. The immediate priority is for platform or data engineering teams to inventory all Avro tables, focusing on those with the `avro.schema.url` property, and for security teams to confirm network reachability and assess the business criticality of these tables. Identifying the accountable owner for each affected table and its data is crucial before planning remediation, which may involve vendor coordination or careful maintenance window planning.

Data platform or engineering teams own resolution.
Verify Avro tables with `avro.schema.url` property.
Plan remediation based on table criticality.

Supplementary metadata

CVSS vector

Validate whether this threat affects your internet-facing exposure.

Halo Threat Intelligence helps prioritize remediation with Halo Surface Signal and H/A/L/O context. Start exposure validation with a free external attack surface trial.

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Frequently asked questions

What is Apache Hive?

Apache Hive is a data warehouse software built on top of Hadoop that facilitates querying and managing large datasets stored in distributed storage. It provides a structured interface, similar to SQL, to process and analyze massive amounts of data. Users create tables to organize this information, often utilizing different data formats like Avro, which requires specific schema definitions to interpret the stored information correctly during query operations.

What is the vulnerability behind CVE-2026-55976?

This CVE involves a Server-Side Request Forgery (SSRF) weakness, categorized as CWE-918. It occurs when a web application can be manipulated to send requests to unintended locations. In this case, Hive's schema resolution process can be tricked into fetching data from a user-supplied URL. Instead of just accessing the intended schema, the server acts on the attacker's behalf to interact with internal network services, local files, or cloud metadata endpoints.

How does an attacker trigger this SSRF flaw?

An attacker needs valid authentication and the privilege to create tables. The trigger occurs when they set the 'avro.schema.url' property for a new Avro table to a malicious URL. The bug is activated when the Hive server attempts to resolve that URL during a query. Simply having access to Hive is not enough; the attacker must be able to define table properties. If the 'avro.schema.url' property is not used or is restricted to trusted locations, the trigger path is effectively blocked.

Is my environment at risk from this Hive vulnerability?

Risk depends on your specific setup. According to Halo Surface Signal, this is unlikely to be a high-exposure issue because it requires valid authentication and specific table creation privileges. Hive is also typically placed deep within internal networks rather than facing the internet. However, you should evaluate if users with table creation rights could potentially access sensitive cloud metadata or internal services from the Hive server process.

How should I respond to CVE-2026-55976?

The primary response is to upgrade your Apache Hive deployment to version 4.2.1 or later. Before patching, data engineering teams should audit their current environment by identifying all Avro tables that utilize the 'avro.schema.url' property. Monitoring logs for unusual outbound connection attempts or unexpected URL schemes in table definitions can help identify if any existing tables are misconfigured or being used maliciously.

References

Written by Nicholas Merritt

Nicholas Merritt is VP of Security Solutions at Halo Security. With more than 25 years across application security, vulnerability prioritization, and offensive security, he helps teams translate threat data into practical exposure validation and remediation focus. He authors Halo Threat Intelligence CVE advisories using Halo Surface Signal and H/A/L/O context to prioritize internet-facing risk.