Unauthenticated TLS 1.3 KeyUpdate record can cause persistent connection retention and DoS in crypto/tls

• cbl2 msft-golang 1.25.8-1 on CBL-Mariner 2.0

• cbl2 golang 1.18.8-10 on CBL Mariner 2.0

• cbl2 golang 1.22.7-5 on CBL Mariner 2.0

• azl3 golang 1.25.8-1 on Azure Linux 3.0

• azl3 golang 1.26.1-1 on Azure Linux 3.0

• cbl2 msft-golang 1.25.8-1 on CBL Mariner 2.0

• azl3 golang 1.25.9-1 on Azure Linux 3.0

• azl3 golang 1.26.2-1 on Azure Linux 3.0

SecurityAlert records field-level changes from the point we begin following a bulletin. Earlier vendor changes may not have a field-by-field record.

1. Oct 8, 2026 at 9:05 AM UTC
   • Severity changed from Medium to High.
   • Added affected products: azl3 golang 1.27.0-1 on Azure Linux 3.0, cbl2 msft-golang 1.25.8-1 on CBL-Mariner 2.0.
   • The vendor changed its remediation guidance.

1. Apr 11, 2026 at 1:07 AM UTC
   Published by Microsoft Security Response Center

   The publication date reported by the vendor.

2. Sep 25, 2026 at 2:42 AM UTC
   Updated by Microsoft Security Response Center

   The vendor changed the advisory after it was first published.

3. Sep 27, 2026 at 11:11 PM UTC
   Added to SecurityAlert

   We collected the advisory from the official source.

4. Nov 10, 2026 at 2:00 AM UTC
   Confirmed at the source

   Our collector saw this advisory during a later source check.