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Firebase PHP-JWT < 6.0.0 — Algorithm Confusion

CVE-2021-46743Published · Updated

Action summary

Affected: ≤2.1.0Update to 2.1.1 or newer

All remediation steps
Watch plugin
Severity
Critical9.1
CVSS
9.1
CVSS 3.1 · CNA (Wordfence)
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N
What does this vector mean?
AV:N Attack vector
Network
AC:L Attack complexity
Low
PR:N Privileges required
None
UI:N User interaction
None
S:U Scope
Unchanged
C:H Confidentiality
High
I:H Integrity
High
A:N Availability
None
Weakness
CWE-843 Access of Resource Using Incompatible Type
Required access
No account needed
Exploit prediction (EPSS)
No score
CISA KEV
Not listed
On this page8

Am I affected?

JWT Auth – WordPress JSON Web Token Authentication jwt-auth

  1. Affected≤ 2.1.0
  2. Patched in2.1.1

Update to 2.1.1 or newer.

You are affected if you run ≤ 2.1.0. Version 2.1.1 and later are not affected by this issue.

  • Check your version: in wp-admin go to Plugins → Installed Plugins and read the version under JWT Auth – WordPress JSON Web Token Authentication.
  • No admin access? Run a passive check of your site. It reads public files only.
  • No account is needed to exploit this. Treat any exposed site on an affected version as at risk.

What to do

  1. Update to version 2.1.1, or a newer patched version
  2. Rotate administrator passwords and application secrets if the site ran a vulnerable version while publicly reachable.
  3. Watch JWT Auth – WordPress JSON Web Token Authentication to get an email when the next vulnerability is published.

Advisory

Source description from Wordfence Intelligence.

In Firebase PHP-JWT before 6.0.0, an algorithm-confusion issue (e.g., RS256 / HS256) exists via the kid (aka Key ID) header, when multiple types of keys are loaded in a key ring. This allows an attacker to forge tokens that validate under the incorrect key. This may or may not be exploitable in WordPress plugins and themes using the library.

Exploits & references

Proof-of-concept & detection

No public proof-of-concept or detection template is known for this vulnerability.

Advisories & patches

More in JWT Auth – WordPress JSON Web Token Authentication

All 2
More vulnerabilities in JWT Auth – WordPress JSON Web Token Authentication
SeverityVulnerabilityCVEPublished
Medium5.3Unauthenticated Persistent Unauthorized Account Access
≤3.0.2No patch available
CVE-2026-106466

Timeline

  1. CVE published

    Severity critical, CVSS 9.1

  2. Record last updated

Sources & licenses

Wordfence record
Vulnerability data
Wordfence Intelligence. [object Object] Licensed under the CC BY-SA 4.0.
CVE® identifiers
[object Object]. Used under the CVE Program. CVE® is a registered trademark of The MITRE Corporation.
CVSS / CWE
National Vulnerability Database (NVD), shown unmodified. This product uses the NVD API but is not endorsed or certified by the NVD.
VulnCrest content
Summary, remediation guidance and page layout © VulnCrest. Not sourced from NVD.

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