CVE-2025-49091 is a vulnerability affecting KDE's terminal emulator Konsole, specifically versions prior to 25.04.2, in conjunction with the KTelnetService component. The issue arises when KTelnetService and a vulnerable Konsole version are installed on a system, but at least one of the programs telnet, rlogin, or ssh is not installed. Under these conditions, a remote attacker can achieve code execution by tricking a user into visiting a malicious website that attempts to load certain URL schemes (such as telnet:) handled by KTelnetService and Konsole. The vulnerability leverages the way these URL schemes are processed, allowing an attacker to execute arbitrary commands on the victim's machine through the terminal emulator. This attack vector requires user interaction, specifically the user allowing the loading of these URL schemes, which may be prompted by the browser or the desktop environment. The vulnerability is classified as low severity by the original advisory, likely due to the required user interaction and specific environment setup. No known exploits are currently reported in the wild. The root cause is related to insufficient validation or sandboxing of URL scheme handlers in Konsole and KTelnetService, which can be abused to execute code remotely. This vulnerability is particularly relevant for Linux desktop environments using KDE Plasma with Konsole as the terminal emulator and KTelnetService installed, but lacking telnet, rlogin, or ssh clients. Patch versions starting from 25.04.2 of Konsole address this issue by fixing the handling of these URL schemes to prevent unauthorized code execution.

For European organizations, the impact of CVE-2025-49091 depends on the prevalence of KDE Plasma desktop environments with Konsole and KTelnetService installed, and the absence of telnet, rlogin, or ssh clients. Organizations with developers, system administrators, or users relying on KDE desktops could be at risk if users visit malicious websites that exploit this vulnerability. Successful exploitation could lead to remote code execution on affected endpoints, potentially allowing attackers to execute arbitrary commands, compromise user data, or pivot within the network. However, the requirement for user interaction and specific software configurations limits the scope and ease of exploitation. The impact on confidentiality, integrity, and availability could be significant on compromised systems, especially if attackers gain elevated privileges or use the foothold to deploy further malware. European organizations with high security standards and controlled desktop environments may face lower risk, but those with less restrictive browsing policies or diverse Linux desktop deployments should be vigilant. The vulnerability could be leveraged in targeted phishing or watering hole attacks against high-value targets using KDE desktops.

1. Upgrade Konsole to version 25.04.2 or later immediately to apply the official patch that addresses this vulnerability. 2. Audit systems to identify installations of KTelnetService and Konsole versions prior to 25.04.2, especially where telnet, rlogin, or ssh clients are not installed. 3. Restrict or disable the handling of telnet:, rlogin:, and ssh: URL schemes in browsers and desktop environments where possible to prevent automatic invocation. 4. Educate users about the risks of clicking on untrusted links, especially those that may trigger terminal or shell commands. 5. Implement endpoint security controls that monitor and block suspicious command executions originating from browsers or URL handlers. 6. Employ network-level protections such as web filtering and URL reputation services to block access to known malicious sites. 7. For organizations using KDE desktops, consider deploying configuration management policies that disable or tightly control KTelnetService usage. 8. Monitor security advisories from KDE and related projects for updates or additional patches. 9. Conduct penetration testing or red team exercises simulating this attack vector to validate defenses and user awareness.