CVE-2026-111065 in aiohttp
Summary
by MITRE • 10/19/2026
AIOHTTP is an asynchronous HTTP client/server framework for asyncio and Python. Prior to 3.14.4, Max-Age processing can overflow and skip closing a connection. An attacker can consequently exhaust the connection pool temporarily until garbage collection resolves the connections. This issue is fixed in version 3.14.4.
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Analysis
by VulDB Data Team • 10/19/2026
The AIOHTTP library serves as a foundational asynchronous HTTP client and server framework for Python, leveraging the asyncio event loop to handle network operations efficiently. In versions prior to 3.14.4, a critical logic error exists within the handling of HTTP connection pooling, specifically concerning the processing of the Max-Age directive found in Cache-Control headers. This vulnerability stems from an integer overflow condition that occurs when calculating the remaining lifetime of a pooled connection based on server-provided cache control directives. The flaw allows for scenarios where the calculated expiration time becomes invalid or negative due to arithmetic errors during type conversion or boundary checks, leading to incorrect state management within the connector's internal pool structure.
From a technical perspective, this integer overflow results in the failure to properly close idle connections that should have been terminated based on their age relative to the Max-Age value. Instead of releasing these resources back into the available pool for reuse or closing them entirely if they exceed their allowed lifespan, the framework retains references to these sockets indefinitely until Python's garbage collector eventually reclaims the memory associated with the connection objects. This behavior creates a resource leak where active socket descriptors are held open unnecessarily, preventing the operating system from reclaiming file descriptors and keeping network ports occupied by stale or invalid connections.
The operational impact of this vulnerability is primarily characterized by temporary exhaustion of the local connection pool resources. As an attacker or high-volume traffic pattern triggers repeated requests that result in these malformed Max-Age calculations, the number of leaked socket references grows rapidly. This leads to a degradation in service availability as new incoming requests cannot be assigned to existing connections and must wait for either garbage collection cycles to clear the stale objects or until the system hits file descriptor limits imposed by the operating environment. While this does not typically allow for remote code execution, it effectively enables a denial-of-service condition against services relying on AIOHTTP for high-throughput asynchronous communication, particularly in environments with limited connection pool sizes or strict resource constraints.
This issue aligns with CWE-190, which describes integer overflow or wraparound errors that can lead to unexpected behavior and resource exhaustion. Furthermore, the exploitation vector relates to ATT&CK technique T1499, Endpoint Denial of Service, specifically under subcategories involving service disruption through resource consumption. The vulnerability highlights the importance of rigorous input validation and bounds checking when processing external HTTP headers that influence internal state management logic in asynchronous frameworks.
To mitigate this risk, organizations utilizing AIOHTTP must upgrade to version 3.14.4 or later, where the integer overflow has been corrected and connection lifecycle management adheres strictly to expected protocol behaviors. For systems unable to immediately patch, implementing rate limiting on incoming requests can help reduce the frequency of trigger conditions, while monitoring file descriptor usage and socket states provides early detection indicators for potential exploitation attempts. Regular auditing of third-party dependencies is essential to ensure that such low-level logic errors in networking libraries do not compromise the stability and availability of critical backend services.