CVE-2026-128131
AIOHTTP: Concatenated compressed streams cause excessive CPU use
AIOHTTP is an asynchronous HTTP client/server framework for asyncio and Python. Prior to 3.14.4, aiohttp decompresses each member of a payload containing many concatenated gzip, deflate, or zstd streams by passing the entire remaining input to a new decompressor, causing quadratic CPU use. Empty members produce no output, so client_max_size and output backpressure do not limit the work. A remote attacker can block a server event loop with a crafted compressed request body or WebSocket message, and a malicious server can similarly block a client. 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-h4cc-hm5h-fmm9CNA: GitHub_M · x_refsource_CONFIRM
- https://github.com/aio-libs/aiohttp/pull/13362CNA: GitHub_M · x_refsource_MISC
- https://github.com/aio-libs/aiohttp/pull/13391CNA: GitHub_M · x_refsource_MISC
- https://github.com/aio-libs/aiohttp/commit/d041d4d0fd48c3f0832084d33be16cf1c4835f85CNA: GitHub_M · x_refsource_MISC
- https://github.com/aio-libs/aiohttp/commit/d925a80539ffd227da1d93ab4a5bff123cc777dbCNA: GitHub_M · x_refsource_MISC
- https://github.com/aio-libs/aiohttp/releases/tag/v3.14.4CNA: GitHub_M · x_refsource_MISC
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