CVE-2026-75936 in ion-java
Summary
by MITRE • 08/18/2026
Improper handling of highly compressed data in the GZIP auto-decompression handler in Amazon ion-java before 1.12.0 might allow remote actors to cause a denial of service via a crafted compressed Ion document that expands to an arbitrarily large size upon decompression.
To remediate this issue, users should upgrade to version 1.12.0 and configure withGzipDecompressionEnabled(false) and/or set an explicit withMaximumBufferSize() when parsing untrusted input.
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Analysis
by VulDB Data Team • 08/18/2026
The vulnerability identified in Amazon ion-java prior to version 1.12.0 stems from a critical flaw in the GZIP auto-decompression handler, specifically categorized under CWE-409 as Improper Handling of Highly Compressed Data. This architectural weakness allows remote attackers to exploit the decompression mechanism by submitting crafted Ion documents that are heavily compressed but designed to expand into an arbitrarily large size upon processing. The core technical issue lies in the absence of effective limits on the output buffer size during the decompression process, which means the application does not validate or constrain the potential expansion ratio before allocating memory for the expanded data. This lack of validation creates a direct pathway for resource exhaustion attacks where the system is forced to allocate excessive amounts of heap space to accommodate the inflated payload.
From an operational perspective, this vulnerability poses a significant risk of denial of service against applications that rely on ion-java for parsing Ion format data. When a malicious actor submits a specially crafted compressed document with a high expansion ratio, the Java Virtual Machine attempts to decompress it into memory without restriction. This rapid consumption of available system resources leads to severe performance degradation or complete application crash due to OutOfMemoryError conditions. The impact is particularly acute in environments where untrusted input is processed automatically by the library, as there is no inherent safeguard to halt processing when the uncompressed size exceeds reasonable thresholds. Such attacks can disrupt service availability for legitimate users and increase infrastructure costs through resource spikes if deployed at scale.
This type of vulnerability aligns with known attack patterns found in industry frameworks such as MITRE ATT&CK, specifically relating to Resource Hijacking or Denial of Service techniques where attackers leverage inefficient algorithmic complexity or lack of input validation to exhaust system resources. The failure to implement proper bounds checking on decompressed data is a common pitfall in many parsing libraries and highlights the importance of defensive programming practices when handling external inputs that may involve compression algorithms like GZIP, DEFLATE, or similar techniques known for high expansion ratios.
To remediate this issue effectively, organizations must upgrade their dependencies to version 1.12.0 of ion-java, which includes fixes designed to mitigate these risks through improved internal logic and default safety measures. However, defense in depth is recommended even after upgrading. Developers should explicitly configure the parser by calling withGzipDecompressionEnabled(false) if GZIP support is not strictly required for their use case, thereby removing the attack surface entirely. For scenarios where decompression is necessary, it is imperative to set an explicit maximum buffer size using the withMaximumBufferSize() method during parsing configuration. This ensures that any attempt to expand data beyond a predefined limit will be rejected before significant memory allocation occurs, thus preserving system stability and preventing denial of service conditions caused by maliciously crafted compressed payloads.