Cases3 cases

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1. IL-0512 xpro.mit.edu returned 503 for an hour when its Kubernetes/APISIX origin certificate expired after renewal failed

   MIT Open Learning2026sev1

   Symptoms

   At 3:38 PM EDT on 3 June 2026, alerts fired because both the xPRO production CMS and the main xPRO site at https://xpro.mit.edu were returning 503 errors. Fastly, in front of the site, could not connect to the Kubernetes/APISIX origin, because the origin certificate for xpro-web.odl.mit.edu had expired at 3:29 PM EDT.

   Service outageTLS certificate errors

   Trigger

   The origin certificate xpro-cert for xpro-web.odl.mit.edu, issued on 2026-03-05 with a 90-day validity period, expired at 3:29 PM EDT on 3 June 2026.

   Root cause

   Configuration change

   Component

   cert-managerCDN and edge networkAuthoritative DNS servers and records

   Contributing factor

   No configuration testsMonitoring blind spotChange with a delayed effect

   Detection

   Alerts for the xPRO production CMS and the main xPRO site fired at 3:38 PM EDT on the 503 errors, and a Rootly incident was created at 4:08 PM EDT.

   Remediation

   • Deleted and recreated the stale cert-manager certificate resources so that cert-manager issued a fresh origin certificate

   Action items

   • Remove the backend origin domain from the non-OpenEdX xPRO Fastly TLS subscription, so Fastly manages only xpro.mit.edu
   • Deploy the Pulumi update for the xPRO application in Production
   • Trigger cert-manager renewal of the xPRO certificate after the conflicting Fastly validation CNAME is removed
   • Consider tests or policy checks that keep cert-manager-managed origin domains out of Fastly TLS subscriptions
   • Consider alerting earlier on failed cert-manager CertificateRequests and Orders, so stale ACME failures are found before the certificate expires

   Lessons

   Reading the outage as a failed cert-manager ACME renewal was true but incomplete; the missing part was that Fastly had been set to manage validation for a backend origin domain that belonged to cert-manager. The team concluded that TLS certificates and DNS validation records need guardrails around ownership, and that public Fastly frontend domains and Kubernetes/APISIX origin domains must not be treated as interchangeable service domains in TLS automation.

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2. IL-0405 An expired AWS Load Balancer Controller webhook certificate left no healthy targets and took BSEE SaaS down

   PortSwigger2026

   Symptoms

   From 10:00 UTC on 11 January 2026 every BSEE SaaS instance in PortSwigger's US and Canada regions was unavailable: customers could not open the Web UI or start scans. The platform team learned of it only when customers reported it through support at 09:52 UTC the next day.

   Service outageTLS certificate errors

   Trigger

   The upgrade of the AWS Load Balancer Controller from v1.14.1 to v1.16.0 on 28 November 2025 left an orphaned webhook TLS secret that cert-manager could not renew, and the certificate in it expired on 8 January 2026.

   Root cause

   Breaking change in an upgrade

   Component

   Ingress controllerAdmission webhookcert-managerHelmConfigMaps and SecretsCloud load balancer

   Contributing factor

   Change with a delayed effectMonitoring blind spot

   Detection

   Customers reported the outage through support at 09:52 UTC on 12 January 2026, almost 24 hours after impact began, and the platform team began investigating at 10:00 UTC.

   Remediation

   • Deleted the orphaned aws-load-balancer-tls secrets in the US and Canada clusters
   • Redeployed the AWS Load Balancer Controller configuration with Helm
   • Verified that new certificates were generated and the webhooks worked again

   Action items

   • Audit all clusters for orphaned secrets that have no owning Certificate resource and resolve them
   • Add high-level application access alerting for each SaaS cluster from an external probe

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3. IL-0460 Vault served an expired TLS certificate and almost every GoCardless service pod crash-looped, a 22-minute full outage

   GoCardless2020

   Symptoms

   On Sunday 25 October 2020 the GoCardless API, dashboard, payment pages and partner integrations were all unavailable for 22 minutes, from 07:32 to 07:54 GMT. Automated monitoring paged the on-call engineer at 07:32, a minute after every request to the API had started failing because no healthy backend was left.

   Service outageContainer crash loopTLS certificate errorsCredentials unavailable

   Trigger

   At 07:22 the TLS certificate Vault was still serving expired. cert-manager had already renewed it, but Vault does not load a new certificate without a restart or a SIGHUP.

   Root cause

   Certificate or credential expiry

   Component

   cert-managerSecrets store

   Contributing factor

   Single point of failureMonitoring blind spotUnverified assumptionHarmful manual action

   Detection

   Automated monitoring detected the failing requests and paged the on-call engineer at 07:32. Certificate expiry monitoring existed for the Layer-7 load balancers but did not cover the TCP load balancer that Vault uses.

   Remediation

   • Forced cert-manager to recreate the Vault certificate
   • Restarted the Vault cluster by hand so it loaded the new certificate
   • Deleted some pods of critical workloads to skip their 5-minute exponential backoff

   Action items

   • Check the certificate of the TCP load balancer in front of Vault with the Blackbox exporter, as for the Layer-7 load balancers
   • Deploy the Reloader controller to roll Vault when its certificate data changes
   • Change theatre-envconsul so envconsul no longer manages the child process and only injects secrets at container startup

   Lessons

   A system that almost every service depends on, such as the secrets store, can take everything down at once, and failure scenarios like Vault becoming unreachable had not been tested enough. Assuming the certificate had expired, when it had been renewed but not reloaded, added a slow and unnecessary recreation step to the recovery.

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