Bug 2573471 (CVE-2026-128127)

Summary: CVE-2026-128127 aiohttp: aiohttp: Denial of Service via crafted base64 multipart request
Product: [Other] Security Response Reporter: OSIDB Bzimport <bzimport>
Component: vulnerabilityAssignee: Product Security DevOps Team <prodsec-dev>
Status: NEW --- QA Contact:
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Priority: high    
Version: unspecifiedKeywords: Security
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OS: Linux   
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A flaw was found in aiohttp. A remote attacker can cause a Denial of Service (DoS) by sending a specially crafted multipart HTTP request containing base64-encoded data. When processing these parts, the application fails to enforce payload size limits while attempting to align base64 data chunks. This failure can bypass configured request size limits, resulting in excessive memory usage or halting server request processing.
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Description OSIDB Bzimport 2026-11-13 20:41:27 UTC 
AIOHTTP is an asynchronous HTTP client/server framework for asyncio and Python. Prior to 3.14.4, BodyPartReader.read_chunk() processing a multipart part with Content-Transfer-Encoding set to base64 keeps reading until the chunk length is a multiple of four without enforcing a byte limit. A short Content-Length or a long run of whitespace can cause one call to read the remaining body into memory before the size check or spin on the event loop. A remote attacker can send such a multipart request to a handler that reads multipart data and bypass client_max_size. This issue is fixed in version 3.14.4.