JWT private key disclosed
Summary: PortSwigger Research describes a JWT flaw in which a misconfigured server includes private key components in the optional "jwk" header of tokens it issues, defined in RFC 7517 and used to carry key data for algorithms such as HMAC or RSA. A malicious user who obtains those private keys could tamper with JWT signatures and impersonate other users.
What's compelling: A leaked signing key in a token header lets an attacker forge identities rather than break in, so the exposure is silent and the blast radius is every user the key can impersonate.
Read the original at PortSwigger Research ↗
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