Attack Chain

1. Attacker crafts a malicious Kiro IDE workspace containing a specially crafted color theme name designed to inject arbitrary code.
2. The malicious workspace is distributed to a target user via social engineering or other means.
3. The user opens the workspace within a vulnerable version of Kiro IDE (prior to 0.8.140).
4. Kiro IDE attempts to load the crafted color theme name within the Kiro Agent webview.
5. Due to the lack of proper sanitization, the malicious code embedded within the color theme name is executed in the context of the webview.
6. The attacker achieves arbitrary code execution on the user’s system due to the exploited vulnerability.
7. The attacker leverages the initial code execution to escalate privileges or install persistent backdoors.
8. The attacker gains complete control over the user’s system, enabling data exfiltration, further lateral movement, or other malicious activities.

Impact

Successful exploitation of CVE-2026-5429 can lead to arbitrary code execution on a developer’s machine. This can lead to full system compromise, including sensitive source code theft, credentials compromise, and supply chain attacks if the compromised machine is used to build and deploy software. The vulnerability impacts any user running Kiro IDE versions before 0.8.140 who opens a malicious workspace. The scope and number of potential victims are large, as it affects all users of the vulnerable versions of the Kiro IDE.

Recommendation

• Immediately upgrade Kiro IDE to version 0.8.140 or later to patch CVE-2026-5429 as recommended by the vendor.
• Implement user awareness training to educate users about the risks of opening untrusted workspaces and trusting prompts within Kiro IDE.
• Monitor process creation events for suspicious activity originating from Kiro IDE processes after a workspace is opened, using the detection rule below.
• Deploy the provided Sigma rules to your SIEM to detect potential exploitation attempts within your environment.