CVE-2026-94636 in Thrift
Summary
by MITRE • 10/02/2026
Improper handling of highly compressed data (data amplification), Function call with incorrectly specified arguments, Improper validation of specified quantity in input vulnerability in Apache Thrift py bindings.
This issue affects Apache Thrift: before 0.25.0.
Users are recommended to upgrade to version 0.25.0, which fixes the issue.
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Analysis
by VulDB Data Team • 10/02/2026
The security flaw identified within the Python bindings of Apache Thrift prior to version 0.25.0 represents a critical intersection of input validation failures and resource management errors that can lead to significant service degradation or denial of service conditions. This vulnerability stems from how the library processes incoming data streams, specifically when dealing with highly compressed payloads. The core technical issue involves improper handling of decompressed data volume relative to the original compressed size, commonly referred to as a Zip Bomb or data amplification attack vector. When an attacker submits a maliciously crafted archive that appears small in its compressed form but expands into gigabytes of uncompressed data upon processing, the application allocates memory proportional to this inflated payload without adequate bounds checking. This behavior is compounded by function calls within the binding layer that accept incorrectly specified arguments regarding buffer sizes or iteration counts, further exacerbating the resource consumption issue.
From a technical perspective, the vulnerability aligns with CWE-400, which describes uncontrolled resource consumption, and CWE-20, improper input validation. The root cause lies in the absence of strict limits on the decompression ratio or absolute memory allocation thresholds during the deserialization process. In many implementations of Thrift's Python bindings, the serialization logic assumes that incoming data is well-formed and within expected size parameters. When this assumption is violated by an adversary providing a high-ratio compressed file, the system attempts to allocate contiguous blocks of memory for the expanded content. If the allocated memory exceeds available physical RAM or swap space, the operating system may invoke its Out-Of-Memory killer, terminating critical processes including the Thrift server itself. This results in a complete denial of service for all users relying on that specific instance, disrupting business operations and potentially causing data loss if transactions are interrupted mid-flight.
The operational impact of this vulnerability is severe, particularly for services exposed to untrusted networks or public internet endpoints where attackers can easily submit crafted requests. Beyond the immediate crash of the application server, such resource exhaustion attacks consume significant CPU cycles as the system attempts to decompress and process the massive payload before failing. This not only affects availability but also impacts performance stability by starving other legitimate users of computational resources during an attack window. Furthermore, if the underlying infrastructure relies on auto-scaling mechanisms triggered by memory usage metrics, this vulnerability could inadvertently trigger unnecessary scaling events, leading to increased operational costs without resolving the root cause unless proper input sanitization is implemented at a higher level in the network stack or application gateway.
Mitigation strategies must prioritize both immediate remediation and long-term architectural resilience. The primary recommendation is to upgrade Apache Thrift to version 0.25.0 or later, where these specific flaws in argument handling and compression limits have been addressed by developers through stricter validation routines and memory caps. For environments unable to immediately patch the software, defensive measures should include configuring reverse proxies such as Nginx or HAProxy to enforce strict request body size limits before data reaches the Thrift server. Additionally, implementing rate limiting on endpoints that accept serialized payloads can help mitigate the frequency of attempted attacks. Security teams should also consider deploying Web Application Firewalls configured with rulesets targeting known compression bomb patterns and ensuring that monitoring systems alert on sudden spikes in memory consumption or CPU usage indicative of such exploitation attempts.
This incident underscores the importance of adhering to secure coding practices regarding external data processing, particularly when dealing with binary protocols like Thrift which are often used for high-performance inter-service communication. The vulnerability highlights risks associated with CWE-787 and CWE-134 in contexts where memory management is not explicitly controlled by the developer but delegated to underlying libraries that may lack sufficient safeguards against adversarial inputs. By treating all incoming serialized data as potentially hostile, organizations can significantly reduce their attack surface. Regular security assessments focusing on deserialization logic and resource allocation limits are essential for maintaining robust defenses against evolving threats in distributed systems architectures.