Help thread for DST Root CA X3 expiration (September 2021)

We have some integration in place between Microsoft O365 and Cisco ( IM&P ) Presence. We originally installed the certificate bundle from the link below which included the DST_Root_CA_X3 certificate. I checked the latest bundle from Microsoft, and it contains the same Root certificate with the same expiration.

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HI @thaubein, welcome to the LE community forum :slight_smile:

I think those may be only the CAs MS O365 sites are using.
Those bundles might not include any LE root certs :frowning:


What @rg305 said is correct -- those certificate bundles are "all roots that a certificate used by a Microsoft 365 site might chain up to". Those bundles contain many roots other than DST Root CA X3, so it's safe to assume that Microsoft 365 has handled the upcoming expiration in their own way. Either way, since Microsoft 365 doesn't appear to use Let's Encrypt to issue certs for any of their services, it's not within the purview of this forum.


I have no special requirements, currently my certificate Leaf -> R3-> DST Root CA X3. After DST Root CA X3 expires, will it automatically become Leaf ->R3-> ISRG Root X1? I am just worried that it will affect the use of the website after September 30.

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@fangze217 It now goes directly from R3 to DST Root CA X3?
If so, which ACME client are you using and when/how was that chain built?



I have two questions:

  1. We use the Authority Information Access extension in the certificates to build the full chain. The R3 intermediate points to regardless of if it is signed by the self-signed X1 or the cross-signed X1. Is it possible to update the endpoint to point to the cross-signed X1? It currently returns the self-signed X1.
  2. If a certificate uses the R3 intermediate with the self-signed X1, can we simply forward the cross-signed X1 or do we need to re-generate the certificate? I suspect that it was generated with the cross-signed X1 since we did not specify to use the alternate chain, but I just want to make sure that the two are interchangeable (except by the older devices).



The keypairs of the self-signed X1 and cross-signed X1 certificates are the same. Both can be used to verify the R3 intermediate. (Which makes sense, as currently there also is just a single R3 intermediate cert, not two for each X1 cert.) You can think of the common name of the intermediate/root certificates as the name for the keypair and not as much as the name for a certificate.


Thank you, Osiris.

I guess we can try to create a custom solution to resolve this, but I am hoping that the endpoint can be updated, if only because it is the currently active signer.



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Not sure if it will make any difference, but they are up to: win-acme.v2.1.18.1119


After the expiration of the DST Root CA X3 certificate at 10 pm on 9:30, 2021, will it affect the normal operation of the website? Will my website become an insecure address? I am using win-acme.v2.0.10.444 client, do I need to update? I am worried, my friend.

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Try this to disable use of the expiring R3 in your chain [on Windows servers]:

  • Open certlm.msc, expand the tree for [1] Intermediate Certification Authorities > Certificates and for [2] Untrusted Certificates > Certificates.
  • Drag R3 issued by DST Root CA X3 from [1] to [2], this will disallow the expiring R3. Don't do this for R3 issued by ISRG Root X1
  • Ensure you have R3 issued by ISRG Root X1 installed in Intermediate Certification Authorities > Certificates, if not you can get it from and install it to that store.

Check your served chain again, you may need a reboot.


Operate in your way, remove DST Root CA X3 and add ISRG Root X1. After restarting the server, there is no browser certificate and it is not updated. Do I need to wait until September 30 to change it?

Hi all.

We us the terraform ACME provider
provider "acme" {

server_url = ""


and we are expecting that we may have to update the provider version or options in order to get the new root cert but from the provider docs we cannot see any options or version changes to do this?

We have tested today with a new cert and we are still getting the DST Root CA. Does anyone one now how we can use the acme terraform provider and get the new Root CA?

I have installed R3 issued by ISRG Root X1 in Intermediate Certification Authorities> Certificates and restarted the server. Why is the certificate still DST Root CA X3 in the browser?

Browser might cache the chain.

check it with one of that tools


@mark-summers, that URL will not need to be changed.
It should already be providing the longer life chain.
Please provide the domain, or the chain file your ACME client received, to confirm.

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To be clear I was asking you to disable the R3 (intermediate) certificate issued by DST Root CA X3, not the root certificates (that would break stuff).

There are versions of your chain: the chain served by your web server, and the chain your client (browser) builds. They are not necessarily the same. On your client/desktop machine you can do the same process with the R3, however you can check your web server chain just using SSL Server Test (Powered by Qualys SSL Labs)


Here's a fun video with @aarongable explaining this expiration! DST Root CAX3 Expiration Sept 2021 - YouTube


I have a problem/question with LDAPS and Active Directory for which I use let's encrypt.

  1. I import the newest key/certificate to AD in personal certificates (created today with certbot). The chain of trust is using DST Root X3 (OK)
  2. I disable DST Root X3 on the AD Server: the chain of trust is using ISRG Root X1 (perfect)
  3. any other let's encrypt certificate/key I use for https just works after I e.g. disable the DST in the certificate store in Firefox (all use ISRG Root X1)

3) on the client side (ubuntu server 20.04 with SOGo and LDAPs authentication):
a) with the latest update of ca-certificates, the DST Root X3 was removed from the trusted store.
openssl s_client -showcerts -connect results in

Verify return code: 20 (unable to get local issuer certificate)

I had to manually import the old DST root certificate again. So far so good.

But, what will happen after the 30th of September - I cannot make the certificate used in LDAP to pick the correct chain of trust (to test that after 30th of Sept everything is still fine)
Scenario A:

  1. on the LDAPS AD Server I disable:
  • all DST Root CA X3 certificates (serial 44 af b0 ... f8 40 6b)
  • the "old" R3 intermediate certificate (serial 40 01 75 ... 16 cd df)
  1. on the LDAPS server, when clicking on the chain of trust of my Let's encrypt certificate, I get a valid chain of trust (using the new R3 intermediate certificate (serial 00 91 2b ... a7 5f 5a), and the correct ISRG root certificate

  2. on the LDAPs client (with SOGo) I make sure the ISRG Root X1 is trusted (I get a valid chain of trust using the testing domain/website for the ISRG root certificate). However, I still cannot get a valid chain. I get
    openssl s_client -showcerts -connect

no peer certificate available
No client certificate CA names sent
SSL handshake has read 0 bytes and written 335 bytes
Verification: OK
New, (NONE), Cipher is (NONE)
Secure Renegotiation IS NOT supported
Compression: NONE
Expansion: NONE
No ALPN negotiated
Early data was not sent
Verify return code: 0 (ok)

(so no certificate has been found?)

additionally, when I look at the fullchain.pem file, it seems that ISRG Root X1 is validated by DST Root CA X3 (which will expire end of Sept).

Is this the problem?

While I disabled all DST, and the old R3 on the AD server, on a testing VM I set the date after 30 september, made sure IRSG is imported, and get error 10 (certificate expired). I don't/can't change the date on the server, but it seems to me the certificate will not validate through the correct chain.

2 Questions:

  1. how can I test that I will have a correct chain after 30th of September
  2. how can I create a certificate for LDAPS which also works for linux clients (I read somewhere that LDAPS does not inform the client which CA to use? So how could I assure that?
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