Go team explains its first URGENT-track security release after weak eMudhra certificate keys
Go 1.27.3 and 1.26.10 block eight intermediate certificates after researchers found their keys could be recovered quickly.
The Go Security team has published an account of the expedited security release it shipped on October 19. Mozilla had added eight intermediate certificates issued under an eMudhra root to its revocation list two days earlier, and researchers found that the keys behind them were weak enough to be recovered almost instantly.
Because that root was trusted by most root programs, an attacker holding such a key could in principle have signed a certificate for any domain name. Go ships its own certificate verifier, which Linux builds rely on, so the team released patched versions that refuse certificates chaining to the affected intermediates. The post gives a timeline of roughly seven and a half hours from first notice to public release.
The team also lists lessons from the process: a few release steps took longer than expected, and it intends to pre-announce urgent releases sooner. It plans to work on certificate revocation support for Linux, where no uniform platform mechanism exists.
Developers who run Go programs that make TLS connections, directly or through a dependency such as gRPC, should rebuild with Go 1.27.3 or 1.26.10. The post suggests checking the toolchain version with go version -m on a binary and running govulncheck in binary mode.
Sources
Verified Oct 27, 2026 (official source). gosecuritytlsdevelopertools