CVE-2026-128129 json
AIOHTTP: Unbounded buffering of data received during an upgrade request
published 6d ago modified yesterday also EUVD-2026-125761 , GHSA-pw86-h8fm-j323
Unreviewed: the maintainers' own advisory
Published by the maintainers on their GitHub repository aio-libs/aiohttp. GitHub has not reviewed it into the GitHub Advisory Database, so the affected packages and versions are the maintainers' word. Read the full advisory on GitHub.
- cvss
- 8.2
- version 4.0, CNA
- cisa kev
- Not listed
- not in CISA's catalog
- epss
- 0.6%
- EPSS 0.6% chance of exploitation in 30 days, percentile 51%
- public exploits
- 0
- none known
Summary
AIOHTTP is an asynchronous HTTP client/server framework for asyncio and Python. Prior to 3.14.4, aiohttp buffers all additional connection data received while a request marked for upgrade, such as a WebSocket handshake, is being handled, without a size limit or flow control. A remote attacker can stream data behind an upgrade request to a handler that does not immediately accept or reject the upgrade and cause unbounded memory consumption. This issue is fixed in version 3.14.4.
Patch / fix
- pypi aiohttp 3.14.4
- github.com/aio-libs/aiohttp@3d850ee commit
- github.com/aio-libs/aiohttp@c207cad commit
- github.com/aio-libs/aiohttp#13501 pull request
- github.com/aio-libs/aiohttp#13511 pull request
- github.com/aio-libs/aiohttp/releases/tag/v3.14.4 release
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Check with FencerCISA SSVC
- Exploitation
- none
- Automatable
- no
- Technical impact
- partial
- Assessed
- yesterday
Exploit prediction
0.64% chance of exploitation in the next 30 days, higher than 51% of all scored CVEs (FIRST EPSS, 2026-11-14).
CVSS scores
| assigned by | version | score | vector |
|---|---|---|---|
| CNA | 4.0 | 8.2 | CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N |
| CNA | 4.0 | 8.2 | CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X |
Affected packages
| ecosystem | package | affected | fixed in |
|---|---|---|---|
| pypi | aiohttp | <=3.14.3 |
3.14.4 |
Affected products
- aio-libs aiohttp
Classification
- Weakness
-
- CWE-770 Allocation of Resources Without Limits or Throttling
References
- github.com /aio-libs/aiohttp/pull/13501
- github.com /aio-libs/aiohttp/pull/13511
- github.com /aio-libs/aiohttp/commit/3d850ee9b92573c7e913821cbcb96005beb3f4df
- github.com /aio-libs/aiohttp/commit/c207cadb257e0959b192ffca0548eca8c71eb96a
-
github.com
/aio-libs/aiohttp/security/advisories/GHSA-pw86-h8fm-j323
advisory
- github.com /aio-libs/aiohttp/releases/tag/v3.14.4
Sources
- CVE List CVE-2026-128129
- NVD CVE-2026-128129
- Maintainer advisory GHSA-pw86-h8fm-j323
Fencer Intel keeps one entry per vulnerability: the CVE id wins, then GHSA, and records that alias each other are merged, except that two CVEs always keep separate entries. The same data is available as JSON.
The maintainers of aio-libs/aiohttp published their own advisory on GitHub. Reviewed sources take precedence over it.