CVE-2026-48034: Hulumi Authentication Bypass Vulnerability

CVE-2026-48034 Overview

CVE-2026-48034 affects Hulumi, an open-source toolkit that ships secure-by-default cloud and platform infrastructure components for Pulumi. Versions prior to 1.4.0 contain an access control weakness ([CWE-284]) that permits a bypass via decoy sibling resources targeting a different bucket. An authenticated attacker can leverage this flaw over the network to compromise integrity of resources outside the intended scope. The maintainers patched the issue in version 1.4.0.

Critical Impact
A low-privileged network attacker can bypass Hulumi's secure-by-default guardrails and manipulate resources in unintended buckets, undermining infrastructure-as-code integrity.

Affected Products

Hulumi versions prior to 1.4.0
Pulumi deployments consuming vulnerable Hulumi components
Cloud infrastructure provisioned with affected Hulumi resource definitions

Discovery Timeline

2026-07-24 - CVE-2026-48034 published to NVD
2026-07-28 - Last updated in NVD database

Technical Details for CVE-2026-48034

Vulnerability Analysis

Hulumi provides secure-by-default cloud resource abstractions for Pulumi. The affected versions enforce access control checks that assume sibling resources referenced during evaluation belong to the same protected bucket. Attackers can supply decoy sibling resources pointing to a different bucket, causing the policy layer to authorize operations that should have been rejected.

This is an improper access control weakness classified under [CWE-284]. The flaw resides in the resource resolution logic rather than authentication, so attackers who already possess low-level privileges within the Pulumi environment can abuse it. Successful exploitation impacts the integrity of resources across bucket boundaries and can propagate to downstream components managed by the same stack.

Root Cause

The root cause is trust placed in sibling resource metadata during authorization decisions. Hulumi's checks did not validate that referenced siblings actually resided within the target bucket scope before granting the operation. This allowed an attacker-supplied decoy resource to redirect enforcement to an unrelated bucket, bypassing the intended guardrail.

Attack Vector

The attack vector is network-based and requires low privileges within the Pulumi context. An attacker crafts a resource definition that references a sibling in a bucket the attacker controls or targets. When Hulumi evaluates the policy, the decoy sibling satisfies the check and the operation proceeds against a different bucket than the security model intended.

No verified public exploit code is available for CVE-2026-48034. Refer to GitHub Pull Request #175 and GitHub Pull Request #178 for the technical fix details.

Detection Methods for CVE-2026-48034

Indicators of Compromise

Pulumi stack operations that reference sibling resources residing in buckets outside the expected project scope.
Unexpected modifications to bucket resources not owned by the executing stack or pipeline.
Hulumi component invocations logging cross-bucket resource resolution during policy evaluation.

Detection Strategies

Audit Pulumi state files and preview outputs for resource references that cross bucket boundaries.
Review CI/CD pipeline logs for Hulumi versions below 1.4.0 and flag deployments that predate the patch.
Correlate cloud provider audit logs with Pulumi run history to identify writes to buckets not declared in the stack.

Monitoring Recommendations

Enable cloud provider object storage audit logging and alert on writes originating from Pulumi service principals to unexpected buckets.
Monitor source repositories for Hulumi dependency pins and enforce minimum version 1.4.0.
Track infrastructure-as-code drift with continuous scanning to catch unauthorized cross-bucket changes.

How to Mitigate CVE-2026-48034

Immediate Actions Required

Upgrade Hulumi to version 1.4.0 or later across all Pulumi projects and shared component libraries.
Inventory all Pulumi stacks that import Hulumi and rebuild pipelines against the patched release.
Review recent stack operations for unauthorized cross-bucket resource changes and roll back where necessary.

Patch Information

The maintainers released the fix in Hulumi v1.4.0. Details are documented in GitHub Security Advisory GHSA-9vc9-4jv3-rf86, with code changes in Pull Request #175 and Pull Request #178.

Workarounds

Restrict IAM permissions for Pulumi execution roles so they cannot write to buckets outside their declared project scope.
Add pipeline policy checks that reject Pulumi previews containing sibling resource references crossing bucket boundaries.
Pin Hulumi to >=1.4.0 in dependency manifests to prevent regression to vulnerable versions.

bash

# Configuration example
# Upgrade Hulumi in your Pulumi project
npm install @hulumi/core@^1.4.0
# Or for Python-based Pulumi projects
pip install --upgrade 'hulumi>=1.4.0'