7.5

CVSS Score

3.1

-

CVSS Score

Basic Information

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CVE-2024-12254

CVE-2024-12254: Starting in Python 3.12.0, the asyncio._SelectorSocketTransport.writelines() method would not ...

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.

(GitHub Advisory)

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CVE-2024-12254

CVE-2024-12254:

7.5

CVSS Score

3.1

-

CVSS Score

Basic Information

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Technical Details

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Root Cause Analysis

The vulnerability description and the provided commit patches clearly indicate that the writelines method within the asyncio.selector_events._SelectorSocketTransport class was the source of the vulnerability. The patches show that the fix involved adding a call to _maybe_pause_protocol() inside the writelines method. This function was not correctly handling the write buffer, leading to potential memory exhaustion. The other modified files are test files or NEWS fragments, not part of the vulnerable code itself.

The function asyncio.selector_events._SelectorSocketTransport.writelines is identified as vulnerable because it's the function that, prior to the patch, would not pause writing when the buffer was full. This lack of pausing is the core of the vulnerability, leading to potential memory exhaustion. The patch adds self._maybe_pause_protocol() to this function, which is the mitigation. Therefore, writelines is the function that, when called in its unpatched state, exhibits the vulnerable behavior and would be present in a runtime profile during exploitation (i.e., when the memory exhaustion is occurring due to continuous writing without pausing).

Vulnerable functions

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WAF Rule

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Reasoning

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