CVE-2026-70646 in aiosend
Summary
by MITRE • 08/06/2026
aiosend is a synchronous and asynchronous Crypto Pay API client. Pror to version 3.0.7, `WebhookHandler.feed_update()` deserializes the entire request body before verifying the HMAC signature. This allows an unauthenticated attacker to force expensive parsing of arbitrary JSON payloads that will ultimately be rejected, leading to unnecessary CPU and memory consumption. Version 3.0.7 fixes the issue. Some workarounds are available. Restrict request body size at the reverse proxy or web framework, rate-limit webhook endpoints, and/or reject oversized requests before JSON parsing.
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Analysis
by VulDB Data Team • 08/06/2026
The vulnerability in aiosend versions prior to 3.0.7 represents a critical security flaw that enables resource exhaustion through improper input validation. This issue specifically affects the WebhookHandler.feed_update() method which processes incoming webhook requests from the Crypto Pay API. The flaw stems from a fundamental design error where the system deserializes the complete request body before performing HMAC signature verification, creating an exploitable condition that allows malicious actors to consume excessive computational resources without proper authentication.
This vulnerability operates as a denial of service attack vector by forcing the application to perform expensive JSON parsing operations on arbitrary payloads that will ultimately be rejected due to invalid signatures. The attacker can craft malicious requests with oversized or complex JSON structures that require significant CPU cycles and memory allocation during deserialization. The system processes these requests entirely before validating their authenticity, leading to unnecessary resource consumption that could degrade service performance or even cause complete service unavailability.
From a technical perspective this vulnerability aligns with CWE-400, which addresses "Uncontrolled Resource Consumption" in software systems. The flaw demonstrates poor input handling practices where validation occurs after processing rather than before, creating an opportunity for attackers to exploit computational overhead through crafted payloads. The issue also relates to CWE-347, focusing on "Improper Verification of Cryptographic Signature," as the HMAC verification mechanism is bypassed by prematurely deserializing the request content.
The operational impact of this vulnerability extends beyond simple resource exhaustion to potentially compromise system availability and performance. When exploited at scale, attackers could overwhelm server resources through multiple concurrent webhook requests that consume excessive processing time and memory allocation. This makes the service vulnerable to both accidental and intentional DoS conditions that could affect legitimate users and disrupt normal business operations.
Mitigation strategies for this vulnerability include implementing request size restrictions at the reverse proxy level or within the web framework configuration, which prevents oversized payloads from reaching the application layer. Rate limiting mechanisms should be deployed specifically for webhook endpoints to control the frequency of incoming requests and prevent abuse. Additionally, implementing pre-parsing validation that rejects oversized requests before JSON processing begins provides an effective defense against this particular attack vector. The fix in version 3.0.7 addresses the core issue by ensuring HMAC signature verification occurs prior to any deserialization operations, preventing malicious payloads from consuming system resources unnecessarily.
This vulnerability demonstrates the importance of proper input validation ordering in security-sensitive applications, particularly when dealing with cryptographic verification mechanisms. The remediation approach follows established security principles that prioritize authentication and authorization checks before processing potentially malicious input data. Organizations should consider implementing similar protective measures across their webhook handling systems to prevent similar resource exhaustion attacks, as outlined in the ATT&CK framework's methodology for command and control operations involving resource consumption attacks.