AWS CDK EUVD-2026-95252

Exploitation requires the attacker to control or influence the contents of a directory consumed by CDK asset bundling so that a symbolic link resolving to a file outside the asset tree is present, and requires a developer or CI pipeline to actually run the bundling/synth step (UI:P). Limiting factors: the attack vector is local (AV:L) - it affects the build host, not a deployed/running application - and it depends on CDK following symlinks during bundling output handling; environments that only build from trusted, controlled sources face substantially lower risk. The fix introduces SymlinkFollowMode.BLOCK_EXTERNAL, which throws on external links, so default/hardened configurations on 2.267.0+ block the behavior.

This is a medium-severity, developer/build-time vulnerability rather than a mass-exploitable server flaw, and the signals are internally consistent. The vendor-supplied CVSS 4.0 vector (6.8) uses AV:L and UI:P, meaning exploitation requires local context on the build host plus a developer action (running CDK asset bundling) - it is NOT remotely reachable against a running service. Impact is confidentiality-only (VC:H, VI:N, VA:N), aligning with CWE-59 symlink-following that leaks build-host files into a published asset. No EPSS score was provided, there is no CISA KEV listing, and no public exploit was identified, so there is no evidence of active or widespread exploitation; this reads as a latent supply-chain/CI integrity issue rather than an urgent internet-facing threat. The main caveat: the 'VC:H but SC:N/no scope change' framing arguably understates the blast radius, since leaked build-host secrets (e.g., credentials embedded in a deployed artifact) could enable follow-on compromise - teams using CDK in shared or untrusted-source CI pipelines should prioritize the upgrade accordingly.

An attacker who can influence the contents of a CDK asset source directory (for example via a malicious dependency, a compromised source tree, or an untrusted contribution) plants a symbolic link pointing outside the asset tree. When a developer or CI pipeline runs CDK asset bundling, the link is resolved and a sensitive file from the build host - such as credentials or configuration - is copied into and published as the deployed asset. No public exploit code was identified at time of analysis.