I can confirm the issue :(

Thanks for your report. I've unpushed the Fedora updates.

I see the patch has been backported by upstream into the 45.x branch:
  https://hg.mozilla.org/releases/mozilla-esr45/rev/bf0dd9ae6807

So the next Thunderbird 45.x update will contain the required fix.

I don't know the release schedule. It might be helpful to respin the current Thunderbird build earlier than that date, to allow earlier testing of NSS 3.28

FYI: NSS is required by a set of some more browsers including icecat and seamonkey (I think they'll be similar to firefox and thunderbird) as well as chromium and qtwebengine (don't know if they make a similar test).

I've filed bugs for seamonkey and xulrunner already.

Thanks for the hint, I didn't know we have icecat in Fedora!
I'll file another bug for it and make it block the 3.28.1 update bug.

dnf repoquery --whatrequires "libnss3.so()(64bit)"

(In reply to Christian Dersch from comment #6)
> dnf repoquery --whatrequires "libnss3.so()(64bit)"

No, it's not that simple, that list is too big. The set of affected application is smaller.

The relevant code is in Mozilla network application code, HTTP v2 protocol code.

It is that simple to get a list of candidates ;) icecat is listed there...

please DON'T push to bodhi

We'd like to create a combined update for all related packages, because the NSS packages will use a Conflicts: statement with the earlier version of your package.

firefox-50.1.0-3.fc25 icecat-45.5.1-6.fc25 nss-3.28.1-1.3.fc25 nss-softokn-3.28.1-1.0.fc25 nss-util-3.28.1-1.0.fc25 seamonkey-2.46-3.fc25 thunderbird-45.6.0-5.fc25 xulrunner-44.0-9.fc25 has been submitted as an update to Fedora 25. https://bodhi.fedoraproject.org/updates/FEDORA-2017-e42b513012

firefox-50.1.0-3.fc25 icecat-45.5.1-6.fc25 nss-3.28.1-1.3.fc25 nss-softokn-3.28.1-1.0.fc25 nss-util-3.28.1-1.0.fc25 seamonkey-2.46-3.fc25 thunderbird-45.6.0-5.fc25 xulrunner-44.0-9.fc25 has been submitted as an update to Fedora 25. https://bodhi.fedoraproject.org/updates/FEDORA-2017-e42b513012

firefox-50.1.0-3.fc24 icecat-45.5.1-6.fc24 nss-3.28.1-1.3.fc24 nss-softokn-3.28.1-1.0.fc24 nss-util-3.28.1-1.0.fc24 seamonkey-2.46-3.fc24 thunderbird-45.6.0-5.fc24 xulrunner-44.0-9.fc24 has been submitted as an update to Fedora 24. https://bodhi.fedoraproject.org/updates/FEDORA-2017-bbb320ba18

firefox-50.1.0-3.fc24 icecat-45.5.1-6.fc24 nss-3.28.1-1.3.fc24 nss-softokn-3.28.1-1.0.fc24 nss-util-3.28.1-1.0.fc24 seamonkey-2.46-3.fc24 thunderbird-45.6.0-5.fc24 xulrunner-44.0-9.fc24 has been submitted as an update to Fedora 24. https://bodhi.fedoraproject.org/updates/FEDORA-2017-bbb320ba18

firefox-50.1.0-3.fc24, icecat-45.5.1-6.fc24, nss-3.28.1-1.3.fc24, nss-softokn-3.28.1-1.0.fc24, nss-util-3.28.1-1.0.fc24, seamonkey-2.46-3.fc24, thunderbird-45.6.0-5.fc24, xulrunner-44.0-9.fc24 has been pushed to the Fedora 24 testing repository. If problems still persist, please make note of it in this bug report.
See https://fedoraproject.org/wiki/QA:Updates_Testing for
instructions on how to install test updates.
You can provide feedback for this update here: https://bodhi.fedoraproject.org/updates/FEDORA-2017-bbb320ba18

firefox-50.1.0-3.fc25, icecat-45.5.1-6.fc25, nss-3.28.1-1.3.fc25, nss-softokn-3.28.1-1.0.fc25, nss-util-3.28.1-1.0.fc25, seamonkey-2.46-3.fc25, thunderbird-45.6.0-5.fc25, xulrunner-44.0-9.fc25 has been pushed to the Fedora 25 testing repository. If problems still persist, please make note of it in this bug report.
See https://fedoraproject.org/wiki/QA:Updates_Testing for
instructions on how to install test updates.
You can provide feedback for this update here: https://bodhi.fedoraproject.org/updates/FEDORA-2017-e42b513012

firefox-50.1.0-3.fc25, icecat-45.5.1-6.fc25, nss-3.28.1-1.3.fc25, nss-softokn-3.28.1-1.0.fc25, nss-util-3.28.1-1.0.fc25, seamonkey-2.46-3.fc25, thunderbird-45.6.0-5.fc25, xulrunner-44.0-9.fc25 has been pushed to the Fedora 25 stable repository. If problems still persist, please make note of it in this bug report.

firefox-50.1.0-3.fc24, icecat-45.5.1-6.fc24, nss-3.28.1-1.3.fc24, nss-softokn-3.28.1-1.0.fc24, nss-util-3.28.1-1.0.fc24, seamonkey-2.46-3.fc24, thunderbird-45.6.0-5.fc24, xulrunner-44.0-9.fc24 has been pushed to the Fedora 24 stable repository. If problems still persist, please make note of it in this bug report.

> FYI: NSS is required by a set of some more browsers including icecat and
> seamonkey (I think they'll be similar to firefox and thunderbird) as well as
> chromium and qtwebengine (don't know if they make a similar test).

Chromium and QtWebEngine use NSS only to load the system certificate store, they do everything else with Google's BoringSSL fork of OpenSSL. QtWebEngine stopped using NSS for everything after a previous NSS update (3.21, IIRC) caused similar compatibility issues, Chromium had done it even a bit earlier.

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