Siemens released security updates for several of its SCADA (supervisory control and data acquisition) products for industrial environments, in order to fix critical vulnerabilities that may have been exploited in recent attacks.One of the vulnerabilities allows unauthenticated attackers to remotely execute arbitrary code on a Siemens SIMATIC WinCC SCADA server by sending specially crafted packets to it. The flaw received the maximum severity score of 10 in the Common Vulnerability Scoring System and can lead to a full system compromise.The other vulnerability can also be exploited by unauthenticated attackers by sending specially crafted packets, but to extract arbitrary files from the WinCC server. The flaw has a CVSS score of 7.8.According to the Industrial Control Systems Cyber Emergency Response Team (ICS-CERT), a division of the U.S. Department of Homeland Security, it's likely that attackers are already aware of these vulnerabilities and are exploiting them."Exploits that target these vulnerabilities are potentially available," ICS-CERT said in a security advisory Tuesday. "Indicators exist that this vulnerability may have been exploited during a recent campaign."ICS-CERT did not say to which campaign it was referring, but last month the organization issued an alert about attacks that installed a backdoor program called BlackEnergy on industrial control systems. ICS-CERT had reasons to believe at the time that the campaign also targeted Siemens' SIMATIC WinCC among products from other vendors, although the attack vector for WinCC was unknown.According to an advisory published by Siemens last week, the newly patched flaws affect SIMATIC WinCC 7.3, 7.2, 7.0 SP3, 7.0 SP2 and earlier versions. Versions 8.1, 8.0, 7.1 SP4 and earlier of the SIMATIC PCS 7 distributed control system and version 13 of the TIA Portal engineering software are also affected because they include WinCC.The company released WinCC 7.2 Update 9 and WinCC 7.3 Update 2 to address the flaws. SIMATIC PCS users are advised to upgrade to version 8.0 SP2 with WinCC V7.2 Update 9 or version 8.1 with WinCC V7.3 Update 2. TIA Portal users should upgrade to version 13 Update 6.Siemens is also working on updates for individual PCS components that will be released in the future, namely OpenPCS 7 V8.0.1 Update 5 and V8.1 Update 1; Route Control V8.0.1 Update 4 and V8.1 Update 1 and BATCH V8.0.1 Update 11 and V8.1.1 Update 1.The company advised administrators to run WinCC servers and engineering stations only within trusted networks, to ensure they communicate only through encrypted channels -- by using VPN tunnels or by activating the Encrypted Communications feature in WinCC -- and to restrict access to WinCC servers to trusted entities only. Customers should also use up-to-date application whitelisting software and virus scanners, the company said.The number of attacks against SCADA users has grown this year. Since June, security researchers have identified two malware campaigns targeting such systems: Havex and BlackEnergy.