CVE-2021-41106

What it is

JWT is a library to work with JSON Web Token and JSON Web Signature. Prior to versions 3.4.6, 4.0.4, and 4.1.5, users of HMAC-based algorithms (HS256, HS384, and HS512) combined with `Lcobucci\JWT\Signer\Key\LocalFileReference` as key are having their tokens issued/validated using the file path as hashing key - instead of the contents. The HMAC hashing functions take any string as input and, since users can issue and validate tokens, users are lead to believe that everything works properly. Versions 3.4.6, 4.0.4, and 4.1.5 have been patched to always load the file contents, deprecated the `Lcobucci\JWT\Signer\Key\LocalFileReference`, and suggest `Lcobucci\JWT\Signer\Key\InMemory` as the alternative. As a workaround, use `Lcobucci\JWT\Signer\Key\InMemory` instead of `Lcobucci\JWT\Signer\Key\LocalFileReference` to create the instances of one's keys.

At a glance

Exploitability

Can be exploited locally on the machine with a low-privilege account. Limited direct impact.

Exploit odds

0.2% chance of exploitation in the next 30 days (EPSS).

Fix

A patch, advisory or fixed version is referenced. Upgrade or apply it.

Timeline

1. 2021-09-28 21:15 UTC PublishedDisclosed publicly on CVE.org and NVD
2. 2026-06-17 04:07 UTC Last updatedMost recent change to the record

Why it ranks here

• Exploited in the wild: no, CISA does not list it.
• Exploit odds: 0.2% in the next 30 days (EPSS).
• Severity: 4.4 MEDIUM (CVSS).
• Fix: a patch or advisory is linked.

Details

Published

2021-09-28 21:15 UTC

Last modified

2026-06-17 04:07 UTC

Exploit probability

0.2% · EPSS, next 30 days

Weakness

CWE-345

Record status

Modified

Affected

• Lcobucci Jwt < 3.4.6
• Lcobucci Jwt < 4.0.4
• Lcobucci Jwt < 4.1.5

Attack profile CVSS 3.1 · 4.4

Attack vector

Local

Complexity

Low

Privileges needed

Low

User interaction

None

Scope

Unchanged

Confidentiality

Low

Integrity

Low

Availability

None

Is it in your code?

Hand this to your coding agent. It searches your project for the affected products and checks versions. Nothing leaves your machine.

Read https://cve-list.com/agent/cve/CVE-2021-41106.md and follow it. Check whether this project is affected by CVE-2021-41106. Read only. Don't change anything and don't upload my code. Tell me yes, no or not sure, with the file as proof.

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