CVE-2026-107608 in aws-cdk-lib
Summary
by MITRE • 10/08/2026
Improper link resolution before file access in the asset bundling output handling in AWS aws-cdk-lib before 2.267.0 might allow a context-dependent actor to cause files from the build host to be published as the deployed asset.
To remediate this issue, users should upgrade to version 2.267.0 or later.
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Analysis
by VulDB Data Team • 10/08/2026
The vulnerability identified in AWS CDK Library versions prior to 2.267.0 represents a critical security flaw within the asset bundling mechanism, specifically concerning how file paths are resolved before being written to the deployment output directory. This issue stems from improper link resolution logic that fails to adequately validate or canonicalize symbolic links and relative path references during the build process. When developers utilize constructs such as DockerImageAsset or Asset in their infrastructure-as-code definitions, the CDK synthesizes these assets by executing bundling commands, often involving container builds or file copying operations. The flaw allows a context-dependent actor, typically one with write access to the source directory of an asset being bundled, to manipulate the filesystem structure prior to synthesis. By creating symbolic links that point outside the intended asset boundary and into sensitive areas of the build host's filesystem, such as configuration files containing secrets or other proprietary code, the attacker can trick the bundling process into including these external resources in the final artifact package.
From a technical perspective, this vulnerability is classified under CWE-22: Improper Limitation of a Pathname to a Restricted Directory, also known as path traversal. The core issue lies in the failure to enforce strict containment within the asset's designated root directory during the resolution phase. When the bundling tool encounters a file reference that resolves via a symlink to an absolute or parent-directory path outside the sandboxed environment, it does not reject this operation but instead proceeds to include the target of the link in the output bundle. This behavior violates the principle of least privilege and isolation expected from containerized build environments used by AWS CDK for asset bundling. The attacker leverages standard filesystem features available on most operating systems to create these deceptive links, requiring only local access to the project directory where the CDK application is being synthesized or deployed.
The operational impact of this vulnerability is severe, primarily revolving around unauthorized data exfiltration and potential compromise of downstream deployment targets. If an asset containing sensitive host files is published to AWS S3 as part of a standard deployment pipeline, those secrets become accessible to anyone with read access to the bucket. This can lead to the exposure of database credentials, API keys, private SSH keys, or internal network configurations stored on the build machine. Furthermore, if these assets are subsequently used in environments where they execute code or influence infrastructure behavior, the injected malicious content could facilitate further attacks such as remote code execution or lateral movement within the cloud environment. The risk is amplified in CI/CD pipelines where automated builds occur frequently and may not have rigorous manual review processes for every asset change.
To mitigate this vulnerability, organizations must immediately upgrade aws-cdk-lib to version 2.267.0 or later, as this release includes patches that enforce stricter path validation and prevent the inclusion of files resolved through external symbolic links. In addition to upgrading, teams should implement defensive coding practices by ensuring that asset directories are isolated from sensitive host data during development. Utilizing dedicated build contexts with minimal filesystem exposure can reduce the attack surface. Security monitoring tools should also be configured to detect unusual file access patterns or symlink creations within CI/CD environments. This incident aligns with ATT&CK technique T1564: Host File and Directory Discovery, as it involves an adversary leveraging host-level mechanisms to gather sensitive information for exfiltration through the application's normal operational channels.