CVE-2021-41106

Token forgery via key-path HMAC secret

Published Sep 28, 2021 · Updated Aug 4, 2024

Improper JWT authentication in Lcobucci JWT allows local users to forge HMAC-signed tokens by using a known key-file path as the secret. HMAC signers receive LocalFileReference's path string instead of reading the referenced key contents, making the predictable path the effective signing key. Exploitation requires an application to use HS256, HS384, or HS512 with LocalFileReference, and forged-token privileges remain bounded by claims the consuming application accepts.

CVSS severity4.4
Medium
EPSS probability0.21%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Improper JWT authentication in Lcobucci JWT allows local users to forge HMAC-signed tokens by using a known key-file path as the secret. HMAC signers receive LocalFileReference's path string instead of reading the referenced key contents, making the predictable path the effective signing key. Exploitation requires an application to use HS256, HS384, or HS512 with LocalFileReference, and forged-token privileges remain bounded by claims the consuming application accepts.

The record

CVE
CVE-2021-41106
Published
Sep 28, 2021
Updated
Aug 4, 2024
Vendor
Lcobucci
Product
Lcobucci JWT
Classifications
CWE-345, T1606
Attack vector
local
Privileges
authenticated

Timeline

How it unfolded

  1. Sep 28, 2021CVE publishedPublication date reported by the CVE source.
  2. Aug 4, 2024Record 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=>= 3.4.0, < 3.4.6
  2. Affected versionversion=>= 4.0.0, < 4.0.4
  3. Affected versionversion=>= 4.1.0, < 4.1.5

What conditions does exploitation require?

Attack vectorlocal
Required privilegesauthenticated

What is affected?

Lcobucci · Lcobucci JWTversion=>= 3.4.0, < 3.4.6; version=>= 4.0.0, < 4.0.4; version=>= 4.1.0, < 4.1.5

Published CVSS scores

4.4GitHub Advisory DatabaseCVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:L/I:L/A:N
3.3GitLab Advisory DatabaseCVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:L/A:N

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.

Daily unique IPsNo honeypot observations are available for this CVE in the selected window.

No observations available

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

Weakness, pattern, technique

CWE-345Insufficient Verification of Data Authenticity
T1606Forge Web Credentials

Public exploit references

No public exploit references are available in this record.

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Technologies

Your stack

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Your stack

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