GitHub has disabled SHA-1 in HTTPS

On 15 September GitHub completed a sunset it had scheduled in advance: SHA-1 in HTTPS is now off for github.com and partner CDNs, including Enterprise Cloud and Enterprise Cloud with Data Residency. Enterprise Server is unaffected.²

Relevant to: Anyone whose pipeline still builds on an old base image. A TLS stack that only offers SHA-1 signature algorithms can no longer reach github.com, and it surfaces as a handshake failure in a clone that worked on Monday. Audit the oldest image in your CI first.