CVE-2026-33204Public exploitNetwork attack vector

Unauthenticated service interruption via unbounded PBKDF2 iterations

Published Mar 20, 2026 · Updated Mar 20, 2026

Algorithmic-complexity DoS in Kelvin Mo SimpleJWT before 1.1.1 allows remote attackers to hang PHP workers via crafted PBES2 JWEs. PBES2::generateKeyFromPassword passes the attacker-controlled p2c header directly to hash_pbkdf2 without an iteration ceiling. Any network-facing application that decrypts attacker-controlled JWEs with PBES2 is exposed; repeated invalid tokens consume CPU and hang request workers.

CVSS severity7.5
High
EPSS probability0.48%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Algorithmic-complexity DoS in Kelvin Mo SimpleJWT before 1.1.1 allows remote attackers to hang PHP workers via crafted PBES2 JWEs. PBES2::generateKeyFromPassword passes the attacker-controlled p2c header directly to hash_pbkdf2 without an iteration ceiling. Any network-facing application that decrypts attacker-controlled JWEs with PBES2 is exposed; repeated invalid tokens consume CPU and hang request workers.

The record

CVE
CVE-2026-33204
Published
Mar 20, 2026
Updated
Mar 20, 2026
Vendor
Kelvin Mo
Product
SimpleJWT
Classifications
CWE-400, T1499.004
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Mar 20, 2026CVE publishedPublication date reported by the CVE source.
  2. Mar 20, 2026Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

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Is a vulnerable build present?

Compare these published version ranges with your installed build and any vendor patches.

  1. Affected versionversion=< 1.1.1

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

Kelvin Mo · SimpleJWTversion=< 1.1.1

Published CVSS scores

7.5GitHubCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

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No observations available

Sep 10, 2026Sep 16, 2026
Latest reporting daySep 16, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitPublished

Weakness, pattern, technique

CWE-400Uncontrolled Resource Consumption
T1499.004Endpoint Denial of Service: Application or System Exploitation

Public exploit references

Labels summarize the accepted research assessment. They do not indicate a test against your environment.

Technologies

Your stack

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Your stack

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