CVE-2026-10591: Amazon Kiro IDE File Write Restriction Flaw - What It Means for Your Business and How to Respond

Introduction

CVE-2026-10591 is a high-severity vulnerability in Amazon Kiro IDE, an AI-powered development environment used by software teams across the United States and Canada. The issue can allow attackers to run unauthorized commands on a developer’s machine when certain project folders are opened. Organizations that rely on Kiro for coding, prototyping, or agent-assisted development face potential exposure of source code, credentials, and internal systems. This post explains why the vulnerability matters to business leaders, who is most at risk, and the practical steps you should take. It covers operational, data, reputational, and compliance impacts in clear language, followed by real-world scenarios and a simple checklist to determine if your environment is affected. Technical details appear only in the appendix for security and IT teams.

S1 — Background & History

Amazon published security bulletin 2026-037-AWS on June 2, 2026, addressing CVE-2026-10591. The vulnerability affects Amazon Kiro IDE versions prior to 0.11. Cymulate reported the issue through coordinated disclosure. The Common Vulnerability Scoring System rates it 8.8 (High) under version 3.1 and 8.6 (High) under version 4.0. In plain terms, the flaw involves insufficient restrictions on the IDE’s file-writing capability. Crafted instructions can cause the tool to write files that automatically run code when a developer opens a project folder. Key timeline events include the coordinated report, the June 2 public advisory, and the release of version 0.11 that resolves the problem. Organizations using older builds of this AI coding assistant remain exposed until they upgrade.

S2 — What This Means for Your Business

If your development teams use Amazon Kiro IDE, this vulnerability can disrupt daily operations by allowing unauthorized code to run on workstations that hold proprietary source code and access credentials. Successful exploitation could lead to theft or alteration of intellectual property, exposure of customer or employee data, and compromise of connected systems. Reputation damage follows quickly once news of a developer-machine breach reaches partners or regulators. In the United States and Canada, organizations subject to data-protection rules, contractual security requirements, or industry standards face heightened scrutiny and potential penalties if an incident occurs. Even without confirmed widespread exploitation, the combination of network-reachable attack paths and high impact means delayed response increases both recovery costs and downtime. Treating the issue as a routine software update rather than a business-risk event leaves critical development assets unprotected.

S3 — Real-World Examples

Regional financial services firm: Developers open shared project folders after receiving external documentation or sample code. Malicious instructions cause the IDE to place auto-running configuration files. Attackers gain a foothold on machines that access core banking systems and customer data, triggering regulatory notification duties and temporary suspension of development work.

Mid-sized software product company: An engineering team uses Kiro to accelerate feature delivery. A compromised open-source repository or web page injects instructions that rewrite sensitive project files. Source code and API keys leave the company, forcing a public disclosure, delayed product release, and loss of customer trust.

Healthcare technology provider: Clinicians and developers collaborate on application code that processes protected health information. Exploitation on a single workstation allows lateral movement toward systems holding patient records, creating breach-notification obligations under Canadian and U.S. privacy frameworks and potential contractual penalties with hospital partners.

Government contractor or critical infrastructure supplier: Teams working on regulated projects open folders containing third-party contributions. Unauthorized code execution leads to supply-chain concerns, contract reviews, and possible loss of future bidding eligibility.

S4 — Am I Affected?

• You are running Amazon Kiro IDE version 0.10 or earlier on any desktop or laptop used for development.
• Your developers open project folders that may contain external or untrusted content, including documentation, sample repositories, or web-linked materials.
• Kiro’s agent or file-write features are enabled in the default configuration.
• Workstations running Kiro also hold source code, credentials, or access to production or staging environments.
• Your organization has not completed an inventory of all Kiro installations and verified the installed version is 0.11 or later.
• No compensating controls (such as restricted folder trust settings or network isolation of developer machines) are currently enforced.

Key Takeaways

• CVE-2026-10591 is a high-severity flaw in Amazon Kiro IDE that can lead to unauthorized code execution on developer machines.
• Businesses using older versions face risks to operations, intellectual property, data confidentiality, and regulatory standing.
• Real-world exposure spans finance, software, healthcare, and government supply chains across the United States and Canada.
• Immediate version checks and upgrades to 0.11 or later form the primary defense.
• A structured response that includes inventory, patching, and verification reduces both short-term and long-term exposure.

Call to Action

Confirm your Kiro IDE versions today and apply the available update. If you need independent verification of exposure, configuration review, or a broader assessment of AI-assisted development tooling, contact IntegSec. Our penetration testing team helps organizations identify and reduce cybersecurity risk with practical, prioritized recommendations. Visit https://integsec.com to schedule a discussion tailored to your environment.

TECHNICAL APPENDIX (security engineers, pentesters, IT professionals only)

A — Technical Analysis

The root cause is insufficient access-control restrictions on the file-write tool inside Amazon Kiro IDE prior to version 0.11. The affected component allows the agent to write to execution-sensitive paths such as .vscode/tasks.json. Attack vector is network (remote unauthenticated actors supply crafted instructions). Attack complexity is low. Privileges required are none. User interaction is required (the developer must open the folder). Scope is unchanged. CVSS 3.1 vector is AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H (8.8 High). CVSS 4.0 vector is AV:N/AC:L/AT:N/PR:N/UI:A/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N (8.6 High). The vulnerability maps to CWE-732 (Incorrect Permission Assignment for Critical Resource). Official references include the NVD entry for CVE-2026-10591, AWS security bulletin 2026-037-AWS, and the Kiro 0.11 release notes.

B — Detection & Verification

• Enumerate installed version via the Kiro About dialog or package metadata on Windows, macOS, and Linux.
• Confirm presence of version strings lower than 0.11 in installation directories or application manifests.
• Scanner signatures should flag Kiro IDE packages and version identifiers below the fixed release.
• Log indicators include unexpected writes to .vscode/tasks.json or similar auto-execution configuration files shortly after folder open events.
• Behavioral anomalies appear as spontaneous task execution or process launches tied to project-folder open actions without corresponding user-initiated commands.
• Network indicators may include inbound content that later influences agent file-write operations, though the final execution occurs locally.

C — Mitigation & Remediation

1. Immediate (0–24h): Inventory all Kiro IDE installations and upgrade every instance to version 0.11 or later. Isolate or power off machines that cannot be upgraded within the window if they process sensitive code.
2. Short-term (1–7d): Verify upgrade success across the estate. Review recent project folders for unexpected .vscode/tasks.json or similar files and remove any unauthorized entries. Enforce workspace-trust prompts and restrict opening of untrusted folders. Monitor developer workstations for anomalous process creation.
3. Long-term (ongoing): Maintain a continuous software inventory that includes AI development tools. Subscribe to AWS security bulletins and Kiro release notes. Incorporate agentic IDE configuration reviews into regular security assessments. Apply least-privilege principles to developer accounts and segment networks so that compromised workstations cannot freely reach production systems. Official vendor guidance prioritizes the upgrade; no supported interim workaround exists for environments that cannot patch immediately beyond strict isolation and restricted folder usage.

D — Best Practices

• Restrict the IDE’s file-write capabilities so that execution-sensitive paths cannot be modified by agent actions.
• Require explicit user confirmation before any auto-execution configuration file is created or altered.
• Treat all external content (web pages, repositories, documentation) as untrusted input when feeding an agentic coding assistant.
• Maintain strict version control and rapid patch cycles for AI-powered development tools.
• Combine endpoint detection with developer-workstation monitoring focused on unexpected configuration-file writes and subsequent process launches.