Executive Intelligence Brief

A critical vulnerability, CVE-2026-47891, has been identified in the Spring Framework, a widely-used application framework for Java. This vulnerability has a CVSS score of 9.8, indicating a high severity level. It affects various versions of the Spring Framework, including 5.2.25.RELEASE and earlier, 5.3.0 - 5.3.49, 6.0.0 - 6.0.30, 6.1.0 - 6.1.28, 6.2.0 - 6.2.19, and 7.0.0 - 7.0.8. The vulnerability allows for remote code execution and is caused by the incorrect enforcement of the maxInMemorySize limit in Spring WebFlux applications that rely on the Aalto XML processor. Organizations using affected versions of the Spring Framework should immediately apply patches to mitigate the risk of exploitation.

Threat Overview

The Spring Framework is a popular application framework for Java, widely used for building enterprise-level applications. Its broad deployment footprint and critical role in many organizations' technology stacks make vulnerabilities in this framework particularly concerning. Historically, the Spring Framework has been targeted by threat actors due to its widespread adoption and the potential for high-impact exploits. For instance, previous vulnerabilities in the Spring Framework have led to significant breaches and have been exploited in various campaigns.

Technical Deep Dive

Vulnerability Classification

The vulnerability is classified as CWE-770, which relates to the incorrect enforcement of a resource limit. In this case, the maxInMemorySize limit is not correctly enforced in Spring WebFlux applications that rely on the Aalto XML processor to parse XML input. This can lead to a denial-of-service (DoS) condition or potentially allow for remote code execution (RCE).

Root Cause Analysis

The root cause of this vulnerability lies in the way the Aalto XML processor handles XML input in Spring WebFlux applications. Specifically, the maxInMemorySize limit, which is designed to prevent excessive memory usage, is not correctly enforced. This allows an attacker to craft malicious XML input that can cause the application to consume excessive memory or potentially execute arbitrary code.

Attack Vector & Chain

The attack vector for this vulnerability is network-based, with the attack complexity being low. No privileges are required for exploitation, and user interaction is not needed. The scope of the vulnerability is unchanged, meaning that the exploitation of this vulnerability in one component does not affect other components. The confidentiality, integrity, and availability impacts are all high.

Exploitation Scenario Walkthrough

Scenario: Remote Code Execution via Malicious XML Input

Reconnaissance: An attacker discovers a Spring WebFlux application that relies on the Aalto XML processor to parse XML input. This can be done through various means, such as Shodan scans or exposed API documentation.

Weaponization: The attacker crafts malicious XML input that exceeds the maxInMemorySize limit, potentially allowing for remote code execution.

Delivery & Exploitation: The attacker sends the malicious XML input to the vulnerable application, which processes the input without correctly enforcing the maxInMemorySize limit. This can cause the application to consume excessive memory or execute arbitrary code.

Post-Exploitation: After gaining initial access, the attacker may attempt to escalate privileges, move laterally within the network, or establish persistence mechanisms.

Impact Realization: The final damage may include remote code execution, leading to data exfiltration, ransomware deployment, or supply chain poisoning.

Exploitation in the Wild

There is no indication that this vulnerability is currently being actively exploited in the wild. However, given its high severity and potential impact, it is likely that threat actors will attempt to exploit this vulnerability in the near future.

Impact Analysis

Direct Impact

The direct impact of this vulnerability is remote code execution, which can lead to a complete compromise of the affected application and potentially allow for lateral movement within the network.

Downstream & Cascading Effects

The downstream and cascading effects of this vulnerability may include supply chain risk, regulatory implications, customer data exposure, and operational disruption.

Affected Products & Versions

The following versions of the Spring Framework are affected:

  • Spring Framework 5.2.25.RELEASE and earlier
  • Spring Framework 5.3.0 - 5.3.49
  • Spring Framework 6.0.0 - 6.0.30
  • Spring Framework 6.1.0 - 6.1.28
  • Spring Framework 6.2.0 - 6.2.19
  • Spring Framework 7.0.0 - 7.0.8

Detection & Threat Hunting

Indicators of Compromise

No specific indicators of compromise (IoCs) are provided in the source data.

Detection Rules & Signatures

Detection logic may include monitoring for unusual XML input or excessive memory usage in Spring WebFlux applications.

Threat Hunting Queries

Threat hunting queries may include searching for logs or network telemetry that indicate unusual activity related to XML input processing.

Remediation & Hardening

Immediate Actions (0-24 hours)

Apply patches to affected versions of the Spring Framework:

  • Upgrade to Spring Framework 5.3.50 or later
  • Upgrade to Spring Framework 6.0.31 or later
  • Upgrade to Spring Framework 6.1.29 or later
  • Upgrade to Spring Framework 6.2.20 or later
  • Upgrade to Spring Framework 7.0.9 or later

Short-Term Hardening (1-7 days)

Additional security controls may include:

  • Network segmentation
  • WAF rules to detect and prevent malicious XML input
  • Access restrictions to limit exposure
  • Monitoring enhancements to detect unusual activity

Strategic Recommendations

Long-term architectural and process improvements may include:

  • Regularly updating and patching dependencies
  • Implementing secure coding practices
  • Conducting regular security audits and vulnerability assessments

Analyst Assessment

The risk of exploitation is high due to the critical severity of this vulnerability and its potential impact. Organizations should prioritize patching affected versions of the Spring Framework to prevent potential exploitation.

Sources

  • National Vulnerability Database (NVD)