@mastra/expressnpm
Advisory published Updated
@mastra/express is a confirmed malicious npm package (MAL-2026-6022) that steals credentials and exfiltrates sensitive data (malicious version 1.3.31). Do not install it — remove it immediately and rotate any exposed credentials.
Malicious code in @mastra/express (npm)
What this malware does
The package's bundled distribution files (dist/index.cjs and dist/index.js) contain a Buffer.from(..., 'base64').toString('utf-8') decode pattern. This pattern by itself is benign and extremely common in JavaScript bundles — used for inline data URIs, JWT segment parsing, encoded SVG/PNG assets, configuration constants, and similar legitimate purposes. No corroborating evidence of credential theft, exfiltration, dropper behavior, lifecycle-script abuse, or hardcoded attacker infrastructure was observed. The match is on a single keyword pattern in a bundled main module with no traced harmful execution path.
Any computer that has this package installed or running should be considered fully compromised. All secrets and keys stored on that computer should be rotated immediately from a different computer. The package should be removed, but as full control of the computer may have been given to an outside entity, there is no guarantee that removing the package will remove all malicious software resulting from installing it.
Malicious versions
Indicators of compromise (SHA-256)
Detection & response playbook
Credential / info stealerFind it
Search your lockfiles and build artifacts for @mastra/express (version 1.3.31).
If you installed it — respond
@mastra/express is built to steal secrets, so assume every credential the build or runtime could read is compromised. Remove it from your project and lockfile, then rotate ALL exposed secrets — npm/registry tokens, cloud keys, CI/CD secrets, SSH keys, and any .env values — from a known-clean machine. Audit logs for unauthorized use of those credentials.
Did it already run?
If @mastra/express was installed, its post-install payload may already have run. Removing the package does not undo that — check outbound connections and credential use from the install window onward.
Frequently asked questions
Campaign
References
Credits
- Amazon Inspector · finder
Detect & block this
O3 blocks @mastra/express-class packages before install and in CI — and if it already ran, its runtime egress monitoring catches the credential exfiltration and severs the channel.