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.
The product does not properly control the allocation and maintenance of a limited resource.
| Name | Vendor | Start Version | End Version |
|---|---|---|---|
| Red Hat Enterprise Linux 8 | RedHat | python3.12-0:3.12.8-1.el8_10 | * |
| Red Hat Enterprise Linux 9 | RedHat | python3.12-0:3.12.5-2.el9_5.2 | * |
| Red Hat Enterprise Linux 9.4 Extended Update Support | RedHat | python3.12-0:3.12.1-4.el9_4.5 | * |
| Python2.7 | Ubuntu | bionic | * |
| Python2.7 | Ubuntu | trusty | * |
| Python2.7 | Ubuntu | xenial | * |
| Python3.12 | Ubuntu | noble | * |
| Python3.12 | Ubuntu | oracular | * |
| Python3.13 | Ubuntu | oracular | * |
| Python3.4 | Ubuntu | trusty | * |
| Python3.5 | Ubuntu | trusty | * |
| Python3.5 | Ubuntu | xenial | * |
| Python3.6 | Ubuntu | bionic | * |
| Python3.7 | Ubuntu | bionic | * |
| Python3.8 | Ubuntu | bionic | * |
Mitigation of resource exhaustion attacks requires that the target system either:
The first of these solutions is an issue in itself though, since it may allow attackers to prevent the use of the system by a particular valid user. If the attacker impersonates the valid user, they may be able to prevent the user from accessing the server in question.
The second solution is simply difficult to effectively institute – and even when properly done, it does not provide a full solution. It simply makes the attack require more resources on the part of the attacker.