Python (3.9.5 and 3.9.6 are using Bzip2 1.0.6 which has a known critical vulnerability. 
CVE-2019-12900 (BDSA-2019-1844)
9.8 Critical NVD CVE-2016-3189 (BDSA-2019-2036).

Please upgrade the same to a stable version.

If you update python/cpython-source-deps, I can submit a simple PR to python/cpython.

I want to submit a PR to python/cpython-source-deps, but I think it’s better for a credible person to do this.

I request the dependency update to use bzip2 1.0.8 which is the stable version.

https://github.com/python/cpython-source-deps/pull/25

@ned.deily

Is it possible to update bz2 to 1.0.8 on macOS distribution?
I found the guide to update the library on Windows but for the macOS version, I can not find.

Hmm since I am not a distribution expert, I would like to follow other core devs opinions.

Almost Linux distributions use bzip2 1.0.6 by default.

> Is it possible to update bz2 to 1.0.8 on macOS distribution?

Thanks for looking into this. As I commented on PR 27241, this change is not needed because current macOS python.org installers dynamically link to the system-provided copies of Bzip2; the code to build a private copy of BZip2 in build-installer.py was only used when building on very old versions of macOS, 10.4 and earlier, versions for which we no longer support building installers. I've submitted another PR to remove that unused code to avoid future confusion.

> current macOS python.org installers dynamically link to the system-provided copies of Bzip2

Okay, so this issue looks out of scope to the CPython team if the Windows distribution follows the same policy.

@steve.dowe

Can you check about this issue?

cpython-source-deps was updated middle of last year, but apparently we never merged the main repo change to use it. I'll do it now.

Adding RMs - this should get merged before we do any security releases for issue46948

New changeset 105b9ac00174d7bcc653f9e9dc5052215e197c77 by Steve Dower in branch 'main':
bpo-44549: Update bzip2 to 1.0.8 in Windows builds to mitigate CVE-2016-3189 and CVE-2019-12900 (GH-31731)
https://github.com/python/cpython/commit/105b9ac00174d7bcc653f9e9dc5052215e197c77

New changeset 58d576a43cb1800dd68f06a429d7d41f746a8c01 by Steve Dower in branch '3.10':
bpo-44549: Update bzip2 to 1.0.8 in Windows builds to mitigate CVE-2016-3189 and CVE-2019-12900 (GH-31732)
https://github.com/python/cpython/commit/58d576a43cb1800dd68f06a429d7d41f746a8c01

New changeset 4a3c610cd635f14747cf02c77908e80620aae6ea by Steve Dower in branch '3.7':
bpo-44549: Update bzip2 to 1.0.8 in Windows builds to mitigate CVE-2016-3189 and CVE-2019-12900 (GH-31732) (GH-31735)
https://github.com/python/cpython/commit/4a3c610cd635f14747cf02c77908e80620aae6ea

New changeset e1639f361ee0dfbf08bb8538839d3d557c1a995c by Steve Dower in branch '3.9':
bpo-44549: Update bzip2 to 1.0.8 in Windows builds to mitigate CVE-2016-3189 and CVE-2019-12900 (GH-31732)
https://github.com/python/cpython/commit/e1639f361ee0dfbf08bb8538839d3d557c1a995c

New changeset 6649519e67841b1aa12672f1d9b5cb24494f6196 by Steve Dower in branch '3.8':
bpo-44549: Update bzip2 to 1.0.8 in Windows builds to mitigate CVE-2016-3189 and CVE-2019-12900 (GH-31732) (GH-31734)
https://github.com/python/cpython/commit/6649519e67841b1aa12672f1d9b5cb24494f6196