CVE-2026-33204: SimpleJWT is a simple JSON web token library written in PHP

Q: How do I fix CVE-2026-33204?

simplejwt: upgrade to 1.1.1. Exact commands for each OS are on this page.

Q: Is CVE-2026-33204 being exploited?

CVE-2026-33204 is not on the CISA Known Exploited Vulnerabilities list at the time of the last update. Check again, as this can change.

Q: What does CVE-2026-33204 affect?

CVE-2026-33204 affects simplejwt. Severity is high (CVSS 7.5). 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()

Q: How urgent is CVE-2026-33204?

Priority 47/100. High severity; Public exploit reference; Remotely exploitable, no login, no user action

This week

HIGH 7.5REMOTEUPGRADE

CVE-2026-33204 is a high-severity flaw (CVSS 7.5) affecting simplejwt. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.

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.

Why this priority

High severity
Public exploit reference
Remotely exploitable, no login, no user action

A fixed release or distro patch exists.

Risk facts

CVSS score	7.5 (High)
Attack vector	Network (remote)
Attack complexity	Low
Privileges needed	None
User interaction	None
EPSS exploit chance	0.5% (top 58%)
CISA exploited list	No
Weakness	CWE-400
Published	2026-03-20
Last modified	2026-06-17

Publisher (CNA): GitHub, Inc. · Vendor: kelvinmo

Last updated 2026-06-17 · Sources: CVE Program, NVD, CISA KEV, EPSS and vendor advisories · How we score

Am I affected?

Timeline

2026-03-20 23:16 UTCPublished CVE record published
2026-06-17 10:37 UTCUpdated Record last modified

kelvinmo simplejwt UPGRADE

Affected: < 1.1.1

Fixed in: 1.1.1

Safe to downgrade to: no unaffected older release

1. Check installed version

apt-cache policy simplejwt || rpm -q simplejwt || simplejwt --version

2. UPGRADE to 1.1.1 (Debian / Ubuntu)

sudo apt update && sudo apt install --only-upgrade simplejwt

2. UPGRADE (RHEL / Amazon Linux / Fedora)

sudo dnf upgrade simplejwt

Note

Distros often backport fixes without changing the version number. Confirm with the distro advisory or changelog.

Verify at the official source NVD · CVE Program · Report a problem with this page
Scores and fixes here are computed automatically from those and other public sources. Confirm with the vendor advisory before changing production systems.

Quick answers

How do I fix CVE-2026-33204?

simplejwt: upgrade to 1.1.1. Exact commands for each OS are on this page.

Is CVE-2026-33204 being exploited?

CVE-2026-33204 is not on the CISA Known Exploited Vulnerabilities list at the time of the last update. Check again, as this can change.

What does CVE-2026-33204 affect?

CVE-2026-33204 affects simplejwt. Severity is high (CVSS 7.5). 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()

How urgent is CVE-2026-33204?

Priority 47/100. High severity; Public exploit reference; Remotely exploitable, no login, no user action

Software pages

PHP vulnerabilities

References

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