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CVE-2026-33204

Kelvinmo Simplejwt denial of service

7.5 HIGHPublic exploitEPSS 0.54%
  1. Published20 Mar 2026

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.

CVSS 3.1 breakdown

Attack vectorNetwork
Attack complexityLow
Privileges requiredNone
User interactionNone
ScopeUnchanged
ConfidentialityNone
IntegrityNone
AvailabilityHigh
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

Affected products

Kelvinmo Simplejwt< 1.1.1

Remediation

Fixed in
Kelvinmo Simplejwt≥ 1.1.1

References

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Frequently asked

Is CVE-2026-33204 being actively exploited?

CVE-2026-33204 is not in the CISA KEV catalog. A public exploit reference exists, so treat it as exploitable. Its EPSS exploit probability is 0.54%.

How severe is CVE-2026-33204?

CVE-2026-33204 has a CVSS 3.1 base score of 7.5, rated high. EPSS estimates a 0.54% probability of exploitation.

Which products are affected by CVE-2026-33204?

Affected products include Kelvinmo Simplejwt.

How do I fix CVE-2026-33204?

Upgrade affected software to a fixed version, for example Kelvinmo Simplejwt 1.1.1 or later, then confirm no affected versions remain in your inventory.

How Secuno handles this

Secuno correlates vulnerabilities like CVE-2026-33204 against the real software inventory on every managed device, every day. Rather than a static severity, each match is scored in context: exploit availability, EPSS, the asset's exposure, and business criticality decide where it lands in the queue. If an affected version is present anywhere across your portfolio, it surfaces automatically with a prioritised remediation path.

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Data from the NVD, CISA KEV catalog and FIRST EPSS. CVSS 3.1 base score shown where available.