CVE-2026-33204
Received Received - Intake
Denial of Service in SimpleJWT via JWE PBES2 Header Tampering

Publication date: 2026-03-20

Last updated on: 2026-04-10

Assigner: GitHub, Inc.

Description
SimpleJWT is a simple JSON web token library written in PHP. Prior to version 1.1.1, an unauthenticated attacker can perform a Denial of Service via JWE header tampering when PBES2 algorithms are used. Applications that call JWE::decrypt() on attacker-controlled JWEs using PBES2 algorithms are affected. This issue has been patched in version 1.1.1.
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Meta Information
Published
2026-03-20
Last Modified
2026-04-10
Generated
2026-06-16
AI Q&A
2026-03-21
EPSS Evaluated
2026-06-15
NVD
CVE-2026-33204
Affected Vendors & Products
Showing 1 associated CPE
Vendor Product Version / Range
kelvinmo simplejwt to 1.1.1 (exc)
Helpful Resources
Exploitability
CWE
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KEV
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CWE ID Description
CWE-400 The product does not properly control the allocation and maintenance of a limited resource.
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Executive Summary

This vulnerability exists in SimpleJWT, a PHP library for JSON web tokens. Before version 1.1.1, an unauthenticated attacker could cause a Denial of Service (DoS) by tampering with the JWE header when PBES2 algorithms are used. Specifically, applications that call the JWE::decrypt() function on attacker-controlled JWEs using PBES2 algorithms are vulnerable.

Impact Analysis

The vulnerability can lead to a Denial of Service (DoS) attack, meaning an attacker can disrupt the normal functioning of an application by exploiting the JWE header tampering issue. This can cause the application to become unavailable or unresponsive when processing maliciously crafted JSON web tokens.

Compliance Impact

I don't know

Detection Guidance

I don't know

Mitigation Strategies

To mitigate this vulnerability, upgrade the SimpleJWT library to version 1.1.1 or later, where the issue has been patched.

Additionally, avoid calling JWE::decrypt() on attacker-controlled JWEs using PBES2 algorithms until the upgrade is applied.

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