Is This vulnerability exploited in the wild?

No. Junglewise Threat Intelligence has no report of This vulnerability being exploited in the wild.

How severe is This vulnerability?

High severity, with a CVSS score of 8.7, published 18 June 2026.

Which products and versions are affected?

Web-Token JWT Framework = 4.0.0, = 4.1.0, < 4.1.7.

Is there a fix for This vulnerability?

No fixed version is recorded yet. Check the vendor's advisory in the references below. If you run it, Junglewise drafts a mitigation that fits your setup and applies it once you approve, with senior security engineers behind it.

How is This vulnerability attacked?

It is attacked over the network, in a software library.

Check whether you run Web-Token JWT Framework or Web-Token JWT Library at an affected version. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.

web-token jwt-library denial of service via unbounded PBKDF2 iterations

Q: Is there a fix for This vulnerability?

No fixed version is recorded yet. Check the vendor's advisory in the references below. If you run it, Junglewise drafts a mitigation that fits your setup and applies it once you approve, with senior security engineers behind it.

Q: How is This vulnerability attacked?

It is attacked over the network, in a software library.

Q: Am I affected?

Check whether you run Web-Token JWT Framework or Web-Token JWT Library at an affected version. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.

Severity: high · CVSS 8.7 · Published 2026-06-18

A vulnerability in the web-token PHP JWT library allows an attacker to crash or slow down a server by sending a specially crafted encrypted token. The library fails to limit the number of mathematical iterations used during decryption, allowing a single request to consume excessive CPU resources. This can lead to a denial-of-service (DoS) condition where the server becomes unresponsive to legitimate users.

Technologies: Web-Token JWT Framework, Web-Token JWT Library. Vendors: Web-Token.

Quick answers

Is This vulnerability exploited in the wild?: No. Junglewise Threat Intelligence has no report of This vulnerability being exploited in the wild.
How severe is This vulnerability?: High severity, with a CVSS score of 8.7, published 18 June 2026.
Which products and versions are affected?: Web-Token JWT Framework <= 4.1.6; Web-Token JWT Library < 3.4.10, >= 4.0.0, < 4.0.7, >= 4.1.0, < 4.1.7.
Is there a fix for This vulnerability?: No fixed version is recorded yet. Check the vendor's advisory in the references below. If you run it, Junglewise drafts a mitigation that fits your setup and applies it once you approve, with senior security engineers behind it.
How is This vulnerability attacked?: It is attacked over the network, in a software library.
Am I affected?: Check whether you run Web-Token JWT Framework or Web-Token JWT Library at an affected version. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.

Technical details

The vulnerability exists in the PBES2AESKW::unwrapKey() method of the web-token/jwt-library. When processing JSON Web Encryption (JWE) tokens using password-based algorithms (PBES2-HS*+A*KW), the library reads the 'p2c' (iteration count) parameter directly from the JOSE header without an upper bound. An unauthenticated remote attacker can provide a very large iteration count (e.g., PHP_INT_MAX), forcing the server to perform intensive PBKDF2 computations before authentication or decryption fails. This results in uncontrolled resource consumption (CWE-400). Patches introduce a DEFAULT_MAX_COUNT of 1,000,000 iterations to mitigate the risk.

Affected products

web-token jwt-library < 3.4.10, >= 4.0.0, < 4.0.7, >= 4.1.0, < 4.1.7
web-token jwt-framework <= 4.1.6

Timeline

2026-06-06: disclosed
2026-06-18: advisory

References

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