CVE-2026-128127
AIOHTTP: Base64 multipart parts bypass client_max_size
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.
Fixes and workarounds
No remediation reported in collected sources.
Missing remediation information is not evidence that no patch exists.
Affected products and versions
| Product | Versions | Authority |
|---|---|---|
| aiohttp aio-libs |
< 3.14.4 (affected) | CNA: GitHub_M |
Version ranges are source assertions. Check the vendor advisory and your installed configuration before determining exposure.
CVSS assessments
| Version / score | Vector | Authority |
|---|---|---|
| 4.0 / 8.7 high |
CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N | CNA: GitHub_M |
Exploit evidence
No exploit evidence in collected sources. This is not proof of no exploitation.
References
- https://github.com/aio-libs/aiohttp/security/advisories/GHSA-24c4-3p7v-29cmCNA: GitHub_M · x_refsource_CONFIRM
- https://github.com/aio-libs/aiohttp/pull/13509CNA: GitHub_M · x_refsource_MISC
- https://github.com/aio-libs/aiohttp/pull/13513CNA: GitHub_M · x_refsource_MISC
- https://github.com/aio-libs/aiohttp/commit/2d9c5c1062eff0034fb3ab120897a6c1b3ff7041CNA: GitHub_M · x_refsource_MISC
- https://github.com/aio-libs/aiohttp/commit/a555ab698e08e9baea7386d5b4c0761cb8956fddCNA: GitHub_M · x_refsource_MISC
- https://github.com/aio-libs/aiohttp/releases/tag/v3.14.4CNA: GitHub_M · x_refsource_MISC
For agents and automation
Read public disclosures for free as Markdown or JSON. Compatible browsers also expose native WebMCP tools to search disclosures, read this page, and discover API access.
Use the ontology-linked Cyber API with x402 pay per request, or a Y2 Pro or Elite API key with the intel:cyber scope.
Endpoints and access details
https://api.y2.dev/api/v2/cyber/cveshttps://api.y2.dev/api/v2/cyber/cves/{cveId}
A workspace owner or admin can create a Pro or Elite API key. Send Authorization: Bearer <Y2_API_KEY> from your trusted agent runtime.
For x402, omit Authorization and read the HTTP 402 payment challenge before signing a retry. Public browser tools do not make payments.