External risk intelligence

Apache Fory C++ Deserialization Type Confusion Vulnerability

CVE advisorySeverity: CRITICAL (CVSS 9.8)

CVE-2026-71558

The vulnerability resides in a C++ library used for deserialization. While the attack vector is network-based, the flaw only triggers if an application explicitly utilizes the vulnerable polymorphic smart-pointer deserialization feature to process untrusted data. Since this is not a universal deployment pattern, exposure depends entirely on specific application-level implementation choices.

Deserialization

Apache Fory

0.14.0 to before 1.5.0

Halo Surface Signal: 3 out of 5 — possibly public-facing.

External exposure likelihood

Horizon Alert

Summary of the vulnerability and why it matters

A vulnerability in Apache Fory C++ deserialization allows for potential denial of service or arbitrary code execution through crafted input. This issue could impact systems that use the library's polymorphic smart-pointer deserialization feature to process untrusted data. The main concern is confirming relevance and exposure within our specific applications.

Malicious input could disrupt or control affected systems.
Unpatched libraries create potential security weaknesses.
Verify if this deserialization feature is in use.

Attack Path

How an attacker could exploit the issue

An attacker could reach this vulnerability by sending specially crafted input to an application that uses Apache Fory C++ for deserialization. If the application's deserialization process is not configured to properly validate input types, the attacker's payload could trick the system into misinterpreting data, leading to unexpected behavior. This could potentially allow an attacker to execute arbitrary code or cause a denial of service.

Unauthenticated network access required.
Vulnerable polymorphic smart-pointer deserialization.
Potential for code execution or denial of service.

Live Threat

Current exploitation, exposure, and threat context

This vulnerability could affect systems using Apache Fory C++ when processing specially crafted input through polymorphic smart-pointer deserialization. When type compatibility checks are bypassed, an object of an incompatible type might be treated as the declared base type, leading to unpredictable behavior.

System memory and program integrity.
Malformed input during deserialization.
Denial of service or code execution.

Operational Fix

Recommended remediation, mitigation, and detection steps

This vulnerability affects applications using Apache Fory C++ polymorphic smart-pointer deserialization. Ownership and remediation planning require identifying affected systems, confirming their reachability and business criticality, and then engaging the accountable application or platform teams for coordinated action.

Own by application or platform teams.
Verify polymorphic smart-pointer deserialization usage.
Plan remediation based on identified exposure.

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 Fory C++ used for?

Apache Fory is a C++ library designed to handle complex data structures. Developers typically use it to manage data serialization and deserialization, which allows objects to be converted into a format suitable for storage or network transmission and then reconstructed back into their original state within the application.

What is a heap type confusion vulnerability in CVE-2026-71558?

This is a CWE-502 deserialization weakness. It occurs when the software incorrectly identifies the type of an object during reconstruction. Because the program confuses the actual data type with a different base type, it may access memory in an invalid way, potentially allowing an attacker to manipulate the program's execution flow.

How does an attacker trigger this vulnerability?

An attacker triggers this by sending a specially crafted input payload to an application that processes data using the library's polymorphic smart-pointer deserialization. If your application does not use this specific polymorphic smart-pointer deserialization feature to handle untrusted input, the vulnerability cannot be triggered.

Do I need to worry about CVE-2026-71558?

According to Halo Surface Signal, the risk depends on your specific application implementation. While the vulnerability is network-based, it only poses a threat if your application explicitly uses the vulnerable deserialization feature. You should check your code to see if this feature is active.

How do I fix this Apache Fory C++ issue?

The primary resolution is to update the Apache Fory library to version 1.5.0 or later. Before updating, work with your development or platform teams to identify which applications rely on the affected polymorphic smart-pointer deserialization feature to prioritize remediation.

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.