CVE-1999-1183 is a high-severity remote code execution vulnerability affecting the System Manager (sysmgr) GUI component in Silicon Graphics Inc. (SGI) IRIX operating system versions 6.3 and 6.4. The vulnerability arises because the sysmgr GUI processes certain descriptor files—specifically runtask or runexec files—that define System Manager Tasks. An attacker can craft a malicious descriptor file (a trojan horse runtask or runexec file) that, when processed by the sysmgr GUI, causes arbitrary commands to be executed on the target system. This attack vector leverages the user's Mailcap configuration entries that support the MIME types x-sgi-task or x-sgi-exec, which are used to associate these descriptor files with the System Manager Task execution. Since the vulnerability can be triggered remotely by convincing a user or system to process the malicious descriptor file, it allows unauthenticated attackers to execute arbitrary commands with the privileges of the user running the sysmgr GUI. The CVSS v2 score is 7.6 (high), reflecting network attack vector, high complexity, no authentication required, and complete impact on confidentiality, integrity, and availability. Patches addressing this vulnerability were released by SGI in 1998, with advisories available via SGI's FTP patch servers. There are no known exploits in the wild documented, but the vulnerability remains critical due to its potential impact and ease of exploitation if unpatched. The affected systems are legacy IRIX 6.3 and 6.4 installations, which were primarily used in SGI workstations and servers for high-performance computing and graphics workloads.

For European organizations, the impact of this vulnerability depends largely on the presence of legacy SGI IRIX systems running versions 6.3 or 6.4. Such systems were historically used in specialized sectors like scientific research, engineering, media production, and high-end graphics. If still operational and connected to networks, these systems could be compromised remotely, leading to full system compromise, data theft, or disruption of critical workloads. The vulnerability allows attackers to execute arbitrary commands remotely without authentication, threatening confidentiality, integrity, and availability of the affected systems. This could result in unauthorized access to sensitive data, manipulation or destruction of critical files, and potential pivoting to other network assets. Although IRIX systems are largely obsolete, some European research institutions or media companies might still maintain legacy SGI hardware, making them vulnerable if patches were not applied. The lack of known exploits in the wild reduces immediate risk, but the high severity and ease of exploitation warrant attention in environments where these systems remain in use.

Organizations should first identify any SGI IRIX 6.3 or 6.4 systems within their infrastructure. If such systems are found, immediate application of the official patches released by SGI in 1998 is critical. The patches are available via SGI's FTP servers and should be applied following vendor instructions. If patching is not feasible due to legacy constraints, organizations should isolate these systems from untrusted networks, restrict network access to trusted administrators only, and disable or restrict the use of the System Manager GUI where possible. Additionally, review and harden Mailcap configurations to prevent automatic processing of x-sgi-task or x-sgi-exec MIME types, thereby reducing the risk of malicious descriptor file execution. Network monitoring for unusual activity related to sysmgr processes and descriptor file handling can provide early detection of exploitation attempts. Finally, consider migrating critical workloads off legacy IRIX systems to supported platforms to eliminate exposure to this and other legacy vulnerabilities.