Out-of-bounds read in integrated mimalloc (fixed upstream)
Open
@colesbury is already working on this.
Since May 16, 2025.
3.13
3.14
3.15
interpreter-core
type-bug
- Dominant language
- Python
- Stars
- 77.2k
- Forks
- 35.9k
- PR merge metrics
- PR metrics pending
Description
Bug report
Bug description:
The integrated mimalloc has out-of-bounds bug in the generic implementation of ctz/clz:
https://github.com/python/cpython/blob/6a2296329117463fd09abc73656f1d7b48076100/Include/internal/mimalloc/mimalloc/internal.h#L847-L870
On platforms with 64-bit UL, the multiplication in index calculation can grow much larger than array debruijn[].
It has been fixed in this upstream commit:
https://github.com/microsoft/mimalloc/commit/ed318471126918fce7caf0001cf1e0c78f95173e
CPython versions tested on:
3.14, CPython main branch, 3.13, 3.15
Operating systems tested on:
Linux
Linked PRs
- gh-134149
- gh-134157
Contributor guide
First steps
- Read the whole issue, then the project's contributing guide.
- Comment on the issue to say you are picking it up — it saves two people doing the same work.
- Fork the repository and make your change on a branch.
- Open a pull request that references the issue number.
Assessment
This issue has not been assessed yet.