Updates to the Source and Half-Life 1 Dedicated Server have been released. The updates will be applied automatically when your Steam client is restarted. The specific changes include:

Both:

• Reduced CPU spikes and overall load during server operation
  
• Fixed serveral crash bugs on Linux systems running older GLIBC versions

Half-Life 1 Dedicated Server:

• Clamped the size of the WeaponList network message to prevent a potential buffer overflow exploit (found by Niall FitzGibbon)

News Source: Steam News