TL;DR
An expired SSL certificate for bcr.bazel.build and releases.bazel.build disrupted Bazel users' build workflows after automated renewal failed. A GitHub summary blamed renewal being broken by added subdomains and missing notifications; the incident highlights how certificate expiration can cause abrupt, wide-ranging failures.
What happened
On Boxing Day the Bazel project encountered a service disruption when an SSL certificate for bcr.bazel.build and releases.bazel.build expired, causing registry access and builds to fail with a PKIX certificate validity error. Users saw an error that cited a CertPathValidatorException and a validity check failure when fetching a MODULE.bazel file from the registry. After the immediate problem was mitigated, a summary posted on the project's GitHub issue explained the automated renewal process had been interrupted: new subdomain additions broke the auto-renewal flow and renewal failures did not generate notifications. That left team members who were not familiar with certificate operations scrambling to read documentation and obtain the necessary permissions to restore service. The author of the post argued this example shows how certificate expiration is an abrupt single-point failure and that automation can reduce team familiarity with manual renewal procedures.
Why it matters
- Certificate expiry can trigger a sudden, complete outage for all users relying on the affected endpoints.
- Automated renewal systems can fail silently; missing alerts increase operational risk.
- When routine tasks are automated, teams may lack hands-on experience needed to respond quickly when automation breaks.
- SSL certificate failures do not degrade gradually, making imminent risk hard to detect without proactive monitoring.
Key facts
- Incident reported in a December 27, 2025 post about an outage that occurred on Boxing Day.
- Affected domains were https://bcr.bazel.build and https://releases.bazel.build.
- Users encountered a PKIX path validation error and java.security.cert.CertPathValidatorException: validity check failed while fetching a MODULE.bazel file.
- A GitHub ticket summary stated the auto-renewal was disrupted by new subdomain additions and that renewal failures didn’t send notifications.
- Some Bazel team members unfamiliar with certificate operations had to consult documentation and obtain permissions to fix the problem.
- The author characterized SSL certificates as a technology with failure modes that maximize blast radius when expiry occurs.
What to watch next
- Whether the Bazel project publishes a post-incident report detailing root causes and remediation steps (not confirmed in the source).
- Whether fixes are implemented to ensure subdomain changes do not break automated renewals and to restore effective notification on renewal failures (not confirmed in the source).
- Whether the team adopts additional monitoring or documentation to reduce single-person expertise and improve readiness for certificate issues (not confirmed in the source).
Quick glossary
- SSL/TLS certificate: A digital credential used to authenticate a website and enable encrypted connections between clients and servers.
- Auto-renewal: An automated process that requests and installs renewed certificates before the current ones expire.
- PKIX path validation: A process that validates a certificate chain according to X.509 rules; failures indicate problems with certificate validity or trust.
- Certificate expiration: The timestamp after which a certificate is no longer considered valid; connections relying on an expired certificate can be rejected.
Reader FAQ
What caused the Bazel outage?
An expired SSL certificate for bcr.bazel.build and releases.bazel.build broke registry access and build workflows.
Why did automated renewal fail?
A GitHub summary said the auto-renewal was broken by additions of new subdomains and renewal failures did not send notifications.
Did the outage affect all Bazel users?
The post states the expired certificate broke the build workflow of users who use Bazel; no broader impact scope was provided.
Were key staff out of office and did that cause the delay?
The author noted some team members may have been out for the holiday but said the specifics of team composition and availability were not known.
The dangers of SSL certificates Lorin Hochstein incidents December 27, 2025 2 Minutes Yesterday, the Bazel team at Google did not have a very Merry Boxing Day. An SSL certificate expired…
Sources
- The Dangers of SSL Certificates
- Releases.bazel.build cert expired · Issue #28101
- Bazel Central Registry SSL certificate expired, breaking …
- Preparing for the 47-day certificate era: Why automation …
Related posts
- Rainbow Six Siege outages: accounts flooded with credits and random bans
- How Activists Uncovered the FBI’s COINTELPRO and Security Index
- Porting Windows 2 to the Apricot PC/Xi: bringing Word and Excel aboard