CVE-2026-33204

SimpleJWT has an Unauthenticated Denial of Service via JWE header tampering

HIGH
7.5
CVSS Score
Published: March 20, 2026 at 10:37 PM UTC
Updated: June 17, 2026 at 10:37 AM UTC
1 product affected across 1 vendorSimpleJWT

Using simplejwt by kelvinmo?

Get instant alerts when new vulnerabilities affect simplejwt - before attackers find them.

Real-time alertsTrack your software stackFree plan available
Severity
HIGH7.5
Exploit prediction
EPSS 0.5%
SSVC
PoC

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.

Affected

Our own answer: ranges merged, affected separated from platform-only, with confidence and review flags.

v < 1.1.1
Affected range stops below 1.1.1, so it looks safe — our inference, not a vendor statement

Remediation

No guide yet

No remediation guidance has been written for this CVE yet. What the record does show:

References (2)

x_refsource_CONFIRMExploitVendor Advisory
Source: cverecord
https://github.com/kelvinmo/simplejwt/security/advisories/GHSA-xw36-67f8-339x
x_refsource_MISCProductRelease Notes
Source: cverecord
https://github.com/kelvinmo/simplejwt/releases/tag/v1.1.1

SSVC — Action Prioritization

SSVCPoCAutomatablePartial impact

SSVC signals action urgency (what to patch first), separate from CVSS which measures severity.

CVSS

7.5HIGHGitHub_M
Attack Vector
NETWORK
Complexity
LOW
Privileges
NONE
User Interaction
NONE
Scope
UNCHANGED
Confidentiality
NONE
Integrity
NONE
Availability
HIGH
Vector?

Quick Info

StatusANALYZED
CWE
CWE-400

Get alerted

Stop reading CVE feeds looking for your own stack

Track the products you run and VulnTracker tells you when a new CVE affects them — with what is known about fixing it, and nothing about the rest.

Free plan, no card