Critical incident

Harness: MTLS Outage with Delegates

Affected: Continuous Delivery - Next Generation (CDNG), Continuous Delivery - Next Generation (CDNG), Continuous Delivery - Next Generation (CDNG)

Current status of Harness: Operational — live Harness status

Timeline

1. Sep 14, 2026, 19:00 UTC
   investigating
   We are currently investigating this issue.
2. Sep 15, 2026, 00:42 UTC
   identified
   The issue has been identified and a fix is being implemented.
3. Sep 15, 2026, 00:45 UTC
   identified
   We are continuing to work on a fix for this issue.
4. Sep 15, 2026, 01:46 UTC
   monitoring
   A fix has been implemented and we are monitoring the results.
5. Sep 15, 2026, 03:28 UTC
   resolved
   This incident has been resolved.
6. Sep 21, 2026, 18:26 UTC
   postmortem
   # **Summary** To improve the security posture, On September 14, 2026, Harness performed a scheduled rotation of the TLS certificate used to secure Delegate connections for accounts using mutual TLS \(mTLS\),The replacement certificate passed Harness's existing pre-deployment validation and smoke testing. However, the rotation also introduced a change in certificate authority, which required additional certificate-chain and gateway configuration this prevented affected Delegates from connecting to Harness. Harness has identified the contributing factors and is implementing the corrective actions described below to prevent a recurrence. # **Impact** Delegates configured to use mutual TLS in Prod environment were unable to connect to Harness for until Harness applied a temporary mitigation \(disabling mTLS\) that restored connectivity while the underlying issue was corrected. This affected the ability to run pipelines and other operations dependent on the affected Delegates. Full, permanent connectivity — with mTLS restored to its normal, fully secure configuration — was confirmed for both environments by 7:20 PM PST. # **Root Cause** ‌ As part of routine certificate maintenance, Harness rotated the certificate used by the gateway component that secures mutual TLS connections for Delegates in prod environments. The rotation also introduced a change in certificate authority, which required additional certificate-chain and gateway configuration that was not fully covered by the existing validation process. As a result, the gateway was unable to load the new certificate correctly, and Delegates relying on mutual TLS could not establish a secure connection. # **Remediation** Once the certificate rotation was confirmed as the source of the issue, Harness engineering worked continuously to correct the certificate and validate the fix with Citi before fully restoring the secure configuration. Corrective and Preventive Actions During remediation, Harness also identified and corrected a secondary issue with the replacement certificate's chain, which required an additional deployment before connectivity was fully and permanently restored. # **Next Steps** Harness is taking the following steps to prevent a recurrence of this issue: 1. Extend pre-deployment validation and smoke testing to explicitly cover certificate authority changes and full certificate-chain verification, closing the specific gap that allowed this configuration through. 2. Enhance automation for managing mTLS-related configuration changes, 3. Improve monitoring and alerting for Delegate connectivity, including account-level visibility, so similar issues are detected automatically

Updates as published by Harness (original).