CVE-2026-128127
AIOHTTP: Base64 multipart parts bypass client_max_size
Published Nov 13, 2026
CVSS 4.0 · 8.7 High
EPSS n/a
KEV · Not listed
Description
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.
Analysis
Affected Products
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CVE record
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NVD configurations
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Red Hat packages
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OpenCVE enrichment
No data
Default status is the baseline for the product, each version can override it (e.g. patched versions marked unaffected).
| Vendor | Product | Default status | Versions | ||||||
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| aio-libs | aiohttp | affected |
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No data available yet.
Remediation
Tracking
Advisories
Metrics
Attack Vector Network
Attack Complexity Low
Privileges Required None
Attack Requirements None
User Interaction None
Vulnerable System Confidentiality Impact None
Vulnerable System Integrity Impact None
Vulnerable System Availability Impact High
Subsequent System Confidentiality Impact None
Subsequent System Integrity Impact None
Subsequent System Availability Impact None
No CVSS v3.1
No CVSS v3.0
No CVSS v2
This CVE is not in the KEV list.
No EPSS score available.
Key SSVC decision points have not yet been added.
References
History
Nov 13, 2026 8:45 PM
Description updated. Title updated. Weaknesses updated. Added references. Scoring metrics updated
View changes
| Type | Values Removed | Values Added |
|---|---|---|
| Description | 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. | |
| Title | AIOHTTP: Base64 multipart parts bypass client_max_size | |
| Weaknesses | CWE-400 | |
| References |
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| Metrics |
cvssV4_0
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