CVE-2025-69223 is a vulnerability identified in the aiohttp library, an asynchronous HTTP client/server framework widely used in Python applications leveraging asyncio. Versions prior to 3.13.3 are vulnerable to a denial of service (DoS) attack via a zip bomb—a maliciously crafted compressed payload that, when decompressed, expands exponentially to consume excessive memory resources. The root cause lies in improper handling of highly compressed data (CWE-409) and inadequate resource management (CWE-770), allowing an attacker to send a compressed HTTP request that triggers data amplification during decompression. This can exhaust the host system's memory, leading to service unavailability without requiring any authentication or user interaction. The vulnerability has a CVSS 3.1 base score of 7.5, reflecting its high severity due to network attack vector, low complexity, no privileges required, and no user interaction needed. Although no exploits have been observed in the wild, the potential impact on availability is significant, especially for aiohttp servers exposed to untrusted networks. The issue was publicly disclosed in early 2026 and fixed in aiohttp version 3.13.3. Organizations using aiohttp in web services should assess their versions and apply the patch promptly to mitigate risk.

For European organizations, this vulnerability poses a substantial risk to the availability of web services built on aiohttp. Given the widespread adoption of Python and asyncio frameworks in sectors such as finance, healthcare, government, and technology, a successful DoS attack could disrupt critical applications and services, leading to operational downtime and potential reputational damage. The attack does not compromise confidentiality or integrity directly but can degrade service quality and availability, impacting user experience and business continuity. Organizations with public-facing aiohttp servers are particularly vulnerable, as attackers can exploit the flaw remotely without authentication. The resource exhaustion caused by the zip bomb could also lead to cascading failures in dependent systems or cloud infrastructure, amplifying the impact. Additionally, the lack of known exploits in the wild suggests a window of opportunity for attackers to develop and deploy such attacks, underscoring the urgency for proactive mitigation.

1. Upgrade all aiohttp deployments to version 3.13.3 or later immediately to apply the official fix addressing this vulnerability. 2. Implement strict request size and decompression limits at the application or web server level to prevent processing of excessively large or deeply compressed payloads. 3. Employ web application firewalls (WAFs) or intrusion prevention systems (IPS) capable of detecting and blocking zip bomb patterns or anomalous compression ratios. 4. Monitor server memory usage and application logs for unusual spikes or decompression errors indicative of attempted exploitation. 5. Conduct regular security audits and dependency checks to identify outdated aiohttp versions in development and production environments. 6. Consider isolating aiohttp services in containerized or sandboxed environments with resource quotas to limit the impact of potential DoS attacks. 7. Educate development teams about secure handling of compressed data and encourage adoption of secure coding practices to prevent similar issues.