Collected research

ALPACA: Application Layer Protocol Confusion — Analyzing and Mitigating Cracks in TLS Authentication

ALPACA Attack

Marcus Brinkmann, Christian Dresen, Robert Merget, Damian Poddebniak, Jens Müller, Juraj Somorovsky, Jörg Schwenk and Sebastian Schinzel · alpaca-attack.com

TLS authenticates the certificate but not the TCP endpoint, so a man-in-the-middle can redirect an HTTPS connection to a different service that shares a compatible certificate, such as an FTP or mail server. The mismatched application protocol then reflects or stores attacker data that the browser executes in the web origin, stealing cookies or running script.

Record

Document

ALPACA Attack

Researcher

Marcus Brinkmann, Christian Dresen, Robert Merget, Damian Poddebniak, Jens Müller, Juraj Somorovsky, Jörg Schwenk and Sebastian Schinzel

Published by

alpaca-attack.com

Topic

Identity

In the archive

• Collected in the 2021 research round

Related sources

• USENIX paper and presentation
• Research artifacts
• ALPACA: Application Layer Protocol Confusion - Analyzing and Mitigating Cracks in TLS Authentication
• USENIX Security '21 - ALPACA: Application Layer Protocol Confusion - Analyzing and Mitigating Cracks

Tags

• auth-bypass
• sop-bypass
• xss
• info-leak
• tls
• https
• ftp
• smtp
• large-scale-scan
• prior-art-extension
• owasp-a01-2021
• owasp-a02-2021
• owasp-a03-2021

This page is the archive's own catalogue record. The research is the work of Marcus Brinkmann, Christian Dresen, Robert Merget, Damian Poddebniak, Jens Müller, Juraj Somorovsky, Jörg Schwenk and Sebastian Schinzel, first published at the original source. Preserved copies are kept so the citation survives its host; this one was last captured on 10 August 2026.