CVE-2026-2741: Vaadin Path Traversal Vulnerability

CVE-2026-2741 Overview

CVE-2026-2741 is a Path Traversal vulnerability affecting multiple versions of the Vaadin web application framework. Specially crafted ZIP archives can escape the intended extraction directory during Node.js download and extraction in Vaadin's build process. Vaadin automatically downloads and extracts Node.js if it is not installed locally, creating an attack surface where malicious actors can serve crafted archives containing path traversal sequences that write files outside the intended extraction directory.

The vulnerability can be exploited through various attack vectors including DNS hijacking, man-in-the-middle (MITM) attacks, compromised mirrors, or supply chain attacks. An attacker who can intercept or control the Node.js download can inject malicious content into the build environment.

Critical Impact

Successful exploitation allows attackers to write arbitrary files outside the intended extraction directory, potentially leading to code execution or system compromise during the build process.

Affected Products

• Vaadin 14.2.0 through 14.14.0
• Vaadin 23.0.0 through 23.6.6
• Vaadin 24.0.0 through 24.9.8
• Vaadin 25.0.0 through 25.0.2

Discovery Timeline

• March 10, 2026 - CVE-2026-2741 published to NVD
• March 11, 2026 - Last updated in NVD database

Technical Details for CVE-2026-2741

Vulnerability Analysis

This vulnerability is classified as CWE-22 (Improper Limitation of a Pathname to a Restricted Directory - Path Traversal). The flaw exists in how Vaadin's build tooling handles ZIP archive extraction when downloading Node.js dependencies.

During the build process, Vaadin checks for a locally installed Node.js runtime. If none is found, the framework automatically downloads and extracts Node.js from an external source. The extraction routine fails to properly validate file paths within the archive, allowing entries containing path traversal sequences (such as ../) to write files outside the designated extraction directory.

The attack requires an adversarial position in the network path between the Vaadin build environment and the Node.js download source. This could be achieved through DNS hijacking to redirect requests to an attacker-controlled server, MITM attacks on networks where the build process runs, compromise of legitimate mirror servers, or supply chain attacks targeting package distribution infrastructure.

Root Cause

The root cause is improper input validation during ZIP archive extraction. The extraction process does not sanitize or reject archive entries containing directory traversal sequences like ../ or absolute paths. When these malicious entries are processed, files are written to locations outside the intended extraction directory based on the attacker-controlled path components.

Attack Vector

The attack is network-based and requires the attacker to intercept or control the Node.js download. The exploitation flow involves:

1. The Vaadin build process initiates a download for Node.js
2. An attacker intercepts this request through DNS hijacking, MITM, or compromised infrastructure
3. The attacker serves a malicious ZIP archive containing entries with path traversal sequences
4. The vulnerable extraction routine processes these entries, writing files to attacker-specified locations outside the intended directory
5. Depending on write permissions and target locations, this can lead to arbitrary file overwrite, code injection, or build process compromise

The vulnerability affects build-time operations, meaning development and CI/CD environments are the primary targets. Exploitation is constrained by the requirement for network-level access to intercept downloads.

Detection Methods for CVE-2026-2741

Indicators of Compromise

• Unexpected files appearing outside Vaadin's Node.js extraction directory during builds
• Network traffic to unusual or unauthorized Node.js download sources
• Build logs showing extraction of files with ../ path components
• Modified or new files in parent directories of the expected extraction location

Detection Strategies

• Monitor network traffic from build environments for DNS anomalies or connections to untrusted hosts during Node.js downloads
• Implement file integrity monitoring on build servers to detect unexpected file writes during Vaadin builds
• Review build logs for extraction warnings or errors indicating path traversal attempts
• Use network segmentation and allowlisting to restrict where build processes can download dependencies

Monitoring Recommendations

• Configure build pipelines to verify checksums of downloaded Node.js archives against known-good values
• Implement TLS certificate pinning for Node.js download endpoints where possible
• Deploy intrusion detection rules to alert on ZIP files containing path traversal sequences
• Audit DNS configurations and use DNSSEC to prevent DNS hijacking attacks

How to Mitigate CVE-2026-2741

Immediate Actions Required

• Upgrade Vaadin 14.2.0-14.14.0 to version 14.14.1 or newer
• Upgrade Vaadin 23.0.0-23.6.6 to version 23.6.7 or newer
• Upgrade Vaadin 24.0.0-24.9.8 to version 24.9.9 or newer
• Upgrade Vaadin 25.0.0-25.0.2 to version 25.0.3 or newer
• Use a globally pre-installed Node.js version compatible with your Vaadin version to bypass the vulnerable download mechanism

Patch Information

Vaadin has released patches addressing this vulnerability across all affected version branches. The fixes implement proper path validation during ZIP archive extraction to prevent directory traversal attacks. Multiple pull requests have been merged to address this issue:

• GitHub Pull Request #23125
• GitHub Pull Request #23130
• GitHub Pull Request #23131
• GitHub Pull Request #23133
• GitHub Pull Request #23135

For complete details, refer to the Vaadin CVE-2026-2741 Security Advisory.

Note that Vaadin versions 10-13 and 15-22 are no longer supported. Users on these versions should upgrade to the latest supported version (14, 23, 24, or 25).

Workarounds

• Install Node.js globally on build machines rather than relying on Vaadin's automatic download functionality
• Verify the integrity of Node.js downloads using checksums before allowing extraction
• Implement network controls to ensure Node.js downloads only come from trusted, verified sources
• Use container-based builds with pre-installed Node.js to eliminate the download attack surface

# Install Node.js globally to bypass Vaadin's automatic download
# Example for Ubuntu/Debian systems
curl -fsSL https://deb.nodesource.com/setup_lts.x | sudo -E bash -
sudo apt-get install -y nodejs

# Verify installation
node --version
npm --version

# Vaadin will detect the global installation and skip the download