Download affected certificate serials for 2022.01.25 TLS-ALPN-01 Incident

Last updated:

Update, April 26 2022 We have shut down and removed the configuration and files that powered this web tool. This document will remain as a historical marker.

This page hosts the list of certificates affected by the TLS-ALPN-01 Incident. You can find details about this incident in the community forum and on bugzilla. The list of affected certificates will be available until 25 April 2022. After that date, all affected certificates will be expired.

We have sent notification emails to affected subscribers who have registered a valid email address; if you received an email, you have at least one affected certificate. You may not have received an email if you did not provide an email address when registering your ACME account, if you unsubscribed from Let’s Encrypt email notifications previously, or if the email was caught by a spam filter.

If you are unsure whether your hostname is affected, please use our web tool to investigate the data set. You can also issue requests via a command line interface.

$ curl -X POST -d ''
[]: FQDN was not found in the impacted list.

$ curl -X POST -d ''
[]: The certificate retrieved from your web server has serial 030xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx and was found in our affected data set. Please renew your certificate as soon as possible. Help is available at

$ curl -X POST -d 'serial=03a1c95bdaa36a8268327f2253cbd3ba243'
[03a1c95bdaa36a8268327f2253cbd3ba243]: Serial was not found in the impacted list. No action should be necessary.

$ curl -X POST -d 'serial=030xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx'
[030xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx]: Serial was found in the impacted list. Please renew your certificate as soon as possible. Help is available at

Alternatively, the data set is available for download and local searching.

The file tls-alpn-01-incident-affected-certs-by-regID.csv.gz was a gzipped CSV containing rows in the following format, but is no longer available.


The first column is the ID number of the account which requested issuance of the certificate. The file is sorted by account ID, so all certs issued by a single account are grouped together. The second column is the unique hexadecimal serial number of the certificate. The third column is the time at which the certificate was issued (in RFC3339 format, i.e. YYYY-MM-DDTHH:MM:SSZ, all times UTC). The remaining columns are all identifiers (DNS hostnames) that the certificate was issued for.

You can download this file, unzip it with gunzip or the equivalent utility on your computer, and look up your account id(s). You need to renew and replace each certificate listed, unless you have already done so more recently than Jan 26, 2022, 00:48 UTC.