Collected research

Critical Vulnerabilities in JSON Web Token Libraries

Critical vulnerabilities in JSON Web Token libraries

JWT lets the token itself name the algorithm used to verify it, so an attacker chooses the verification method. Many libraries accepted alg none as a validly signed token, and when handed an HS256 token treated the server's RSA public key as the HMAC secret, letting anyone with the public key forge tokens and authenticate as any user.

Record

Document

Critical vulnerabilities in JSON Web Token libraries

Published by

chosenplaintext.ca

Topic

Other

In the archive

• Collected in the 2015 research round

Related sources

• Critical vulnerabilities in JSON Web Token libraries

Tags

• auth-bypass
• jwt
• privilege-escalation
• mitigation
• owasp-a01-2021
• owasp-a07-2021

This page is the archive's own catalogue record. The research is the work of chosenplaintext.ca, 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.