CVE-2025-30359

What it actually does

This is an information disclosure issue where source code may be exposed when a user accesses a malicious website under vulnerable conditions. The advisory specifically notes risk when applications are built with `output.iife: false`, which can affect how bundled JavaScript is scoped and exposed in a browser context. The provided package metadata maps remediation to the Ubuntu Pro 18.04 LTS `linux-aws-5.4` package, fixed in version `5.4.0-1106.114~18.04.1`; organizations should validate both the affected application build configuration and the listed OS package applicability in their vulnerability management source of truth.

Why it matters to the business

Successful exploitation could allow an attacker to obtain proprietary source code, increasing the risk of intellectual property loss, reverse engineering, discovery of hidden implementation details, and follow-on attacks against exposed logic or secrets accidentally present in code. The current exploitation signal is low: EPSS is 0.00427, it is not listed in CISA KEV, is not associated with ransomware use, and no public exploit maturity is indicated; however, the issue has been public for more than a year, so affected assets should already be remediated through normal patch and build-hardening cycles.

How an attack unfolds

An attacker would host or lure a user to a malicious website designed to interact with a vulnerable browser-executed JavaScript bundle or runtime condition. If the application was built in the vulnerable configuration, such as with `output.iife: false`, the malicious page may be able to access or recover source-code material that should not be exposed. The attacker then collects the disclosed code and analyzes it offline for proprietary logic, embedded secrets, dependency weaknesses, hidden endpoints, or additional vulnerabilities. Where the affected Ubuntu `linux-aws-5.4` package is in scope, remediation should be performed by upgrading to the fixed package version rather than attempting to rely solely on compensating controls.

How to fix it

Upgrade affected Ubuntu Pro 18.04 LTS `linux-aws-5.4` systems to `5.4.0-1106.114~18.04.1` or later through the vendor-supported package channel. Separately, review application build pipelines for use of `output.iife: false`; if the application does not explicitly require this behavior, use a safe bundling configuration and rebuild/redeploy affected front-end assets. Remove source maps or source artifacts from production unless explicitly required and access-controlled. Scan released bundles for embedded secrets, credentials, internal endpoints, and proprietary code comments. Where immediate patching or rebuilds are not possible, restrict access to affected applications, apply browser isolation for high-risk browsing workflows, and monitor for suspicious source-code retrieval patterns.

How to confirm the fix worked

Confirm remediation by checking package inventory and runtime versions for `linux-aws-5.4` and verifying the installed version is `5.4.0-1106.114~18.04.1` or later. For application exposure, inspect webpack or equivalent build configuration for `output.iife: false`, rebuild with the corrected configuration where applicable, and verify deployed JavaScript bundles no longer expose source content unexpectedly. Validate production web roots do not expose source maps, original source files, or build artifacts unless intentionally published. Re-run vulnerability scans, software composition analysis, and package compliance checks after patching. For Ubuntu systems, verify package status using the platform package manager and confirm the running kernel matches the remediated package after reboot where required.

Typical attack path

1. Identify an application or environment using the vulnerable build or affected package version.
2. Prepare a malicious website or page intended to trigger the source-code disclosure condition.
3. Convince a user or automated browser-like process to access the malicious page.
4. Trigger the vulnerable behavior and collect exposed source-code content.
5. Analyze the stolen source code for intellectual property, secrets, hidden endpoints, business logic, or follow-on exploitation opportunities.

How to detect it

Review web proxy, DNS, endpoint browser, and EDR telemetry for users visiting unusual or newly registered websites shortly before or during suspected source-code exposure events. Examine web application logs and CDN logs for unexpected requests to source maps, source files, debug bundles, development artifacts, or JavaScript assets from unfamiliar IP addresses. Inspect endpoint telemetry for browser processes downloading, rendering, or exfiltrating unusually large JavaScript/source artifacts after visiting suspicious pages. Review CI/CD and artifact repositories for evidence that source maps or unminified source bundles were published to production. If source code may have been exposed, search for subsequent suspicious access to internal endpoints, API paths, or secrets that were only discoverable from the source. No reliable CVE-specific network signature or malware artifact is derivable from the provided advisory, so detection should focus on exposure patterns and suspicious source-code access behavior.

What your security team should do

• Prioritize confirming whether the organization uses affected webpack-style build configurations or the listed Ubuntu Pro 18.04 LTS `linux-aws-5.4` package.
• Upgrade `linux-aws-5.4` to `5.4.0-1106.114~18.04.1` or later where the package is present.
• Review build pipelines for `output.iife: false` and rebuild affected production assets using a safe configuration if the setting is unnecessary.
• Search production deployments for exposed source maps, source files, debug bundles, and embedded secrets.
• Treat any confirmed source-code exposure as an intellectual-property incident and perform secret rotation if code may have contained credentials or tokens.
• Because EPSS is low and the vulnerability is not in KEV, handle through standard patch governance unless sensitive source code or high-value applications are exposed.
• Add CI/CD checks that prevent publishing source maps, debug artifacts, or source-containing bundles to unauthenticated production locations.