UNunscaled·Jun 17, 2026
JWT libraries had poor defaults because the spec was poorly designed.
Of course JWT can be implemented securely. Even XMLDSig can be implemented securely. But if the spec is not designed with security and misuse-resistance as a tier 1 priority, you will get more issues. The fact that we didn't see the same sheer volume of issues with PASETO or macaroon libraries (admittedly, the later are far less numerous). I can find only one CVE for a PASETO library from 2020, and this is an issue that has nothing to do with the algorithm itself (JPaseto < 0.3.0 switched the order of two arguments in their hash function call, generating weaker hashes).
The reason PASETO won't have the same issues as JWT is the design (especially with v3/v4). There is no alg=none, symmetric keys are fixed size (so no weak keys can be used) and algorithm confusion is pre
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vented by an explicit implementation guide[1] that strongly mandates that keys for different algorithm version have different types, and verification functions MUST reject a key of the wrong type.
Is JWT safe now? Maybe. A lot of issues have been fixed, but new issues keep coming all the time. We're not even halfway into this year and I can count at least the following serious 2026 CVEs: CVE-2026-28802, CVE-2026-29000, CVE-2026-1529, CVE-2026-22817/8, CVE-2026-34950, CVE-2026-23993, CVE-2026-32597, just to name a few. Most of them are the same classic alg=none, signature verification bypass and algorithm confusion issues.
The issues is that new libraries are coming all the time and the vulnerability elimination process for existing libraries is just a random scattershot. If a security researcher has happened across a vulnerability in library X and reported it, it's solved. If nobody has found it yet: though luck. Unless you pick a library that has been officially audited for these issues, you don't really know if it's truly safe. If you use a PASETO library, it's probably not audited either, but the chance of it having these common types of issues (and other issues, like psychic signatures[2]) are close to nil.
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[1] https://github.com/paseto-standard/paseto-spec/blob/master/d...
[2] https://www.securecodewarrior.com/article/psychic-signatures