CVE-2024-12254
Unbounded memory buffering in SelectorSocketTransport.writelines()
- State
- Published
- Severity
- 8.7 High
- Published
- Dec 6, 2024
- Updated
- Jul 31, 2026
- Reserved
- Dec 5, 2024
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.
Scores
| CVSS | Score | Vector | Source |
|---|---|---|---|
| 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 | PSF |
| 3.1 | 7.5 High | CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H | CISA-ADP |
Weaknesses
Affected Products
| Product | Versions |
|---|---|
CPythonPython Software Foundation |
|
References
- https://github.com/python/cpython/issues/127655issue-tracking
- https://github.com/python/cpython/pull/127656patch
- https://mail.python.org/archives/list/security-announce@python.org/thread/H4O3UBAOAQQXGT4RE3E4XQYR5XLROORB/vendor-advisory
- https://github.com/python/cpython/commit/71e8429ac8e2adc10084ab5ec29a62f4b6671a82patch
- https://github.com/python/cpython/commit/9aa0deb2eef2655a1029ba228527b152353135b5patch
- https://github.com/python/cpython/commit/e991ac8f2037d78140e417cc9a9486223eb3e786patch
- http://www.openwall.com/lists/oss-security/2024/12/06/1
- https://security.netapp.com/advisory/ntap-20250404-0010/
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