Description
Starting in Python 3.12.0, the asyncio._SelectorSocketTransport.writelines() method would not "pause" writing and signal to the Protocol to drain the buffer to the wire once the write buffer reached the "high-water mark". Because of this, Protocols would not periodically drain the write buffer potentially leading to memory exhaustion. This vulnerability likely impacts a small number of users, you must be using Python 3.12.0 or later, on macOS or Linux, using the asyncio module with protocols, and using .writelines() method which had new zero-copy-on-write behavior in Python 3.12.0 and later. If not all of these factors are true then your usage of Python is unaffected.
References (8)
Core 8
Core References
Issue Tracking issue-tracking
https://github.com/python/cpython/issues/127655
Issue Tracking patch
https://github.com/python/cpython/pull/127656
Vendor Advisory
https://security.netapp.com/advisory/ntap-20250404-0010/
Various Sources vendor-advisory
https://mail.python.org/archives/list/[email protected]/thread/H4O3UBAOAQQXGT4RE3E4XQYR5XLROORB/
Scores
CVSS v3
7.5
EPSS
0.0025
EPSS Percentile
48.1%
Attack Vector
NETWORK
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
CISA SSVC
Vulnrichment
Exploitation
none
Automatable
yes
Technical Impact
partial
Details
CWE
CWE-400
CWE-770
Status
published
Products (3)
Python Software Foundation/CPython
3.12.0 - 3.12.9
Python Software Foundation/CPython
3.13.0 - 3.13.2
Python Software Foundation/CPython
3.14.0a1 - 3.14.0a3
Published
Dec 06, 2024
Tracked Since
Feb 18, 2026