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To: cygwin@cygwin.com
Subject: Re: Linux xz issue
Date: Sat, 30 Mar 2024 11:14:53 +0100
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From: Achim Gratz via Cygwin <cygwin@cygwin.com>
Reply-To: Achim Gratz <Stromeko@Nexgo.DE>
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Am 29.03.2024 um 23:43 schrieb Ron Murray via Cygwin:
> There is a serious security issue with xz (and liblzma) versions 5.6.0-1 
> and 5.6.1-1. I note that cywin currently is suggesting an upgrade to 
> 5.6.1-1, which is unsafe. I've looked at the cygwin archives and I don't 
> see a reference to this: sorry if you're already aware of this issue.

Based on what I know so far (and I can't check in detail right now) 
Cygwin is likely not affected: it isn't Linux, nor does it use glibc or 
systemd and also not the patch for OpenSSH that allows the backdoor to 
get activated.  So, the code injection into liblzma5 has very likely not 
been performed during the build (I will check that, but it will take a 
week or so) and even if it did it could not work on Cygwin.

Beyond that, the version 5.4.6 that everybody is currently reverting to 
(and is also still available for Cygwin if you want to go back) was 
already released when the presumed bad actor was co-maintainer and their 
involvement goes back even farther based on the Xz developer mailing 
list.  The repository has been deactivated by GitHub so I can't check 
there, but there is already some discussion about rolling back to 5.3.1 
or thereabouts.

Please note that the account in question has also landed some code in 
libarchive which is likely going to get reverted.  From the looks of it 
there were a few sock-puppet accounts that were supporting the 
activities and it remains to be seen where else these might turn up.

-- 
Achim.

(on the road :-)


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