CVE-2021-38299Network attack vector

Unauthenticated login via missing user presence check

Published Sep 27, 2021 · Updated Aug 4, 2024

Improper authentication in Webauthn Framework 3.3.0 through 3.3.3 allows remote attackers to log in without user presence. The framework fails to verify the user-present bit in signed WebAuthn assertions, allowing an attacker controlling the user's system to request an assertion from an attached FIDO2 authenticator without a physical button press or equivalent presence test. The attacker requires direct control of the user's system and authenticator access; successful use permits login to the relying service, with the record describing authentication bypass rather than independent data or service-impact capabilities.

CVSS severity9.8
Critical
EPSS probability1.80%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
Coverage for this vulnerability

See if you're affected

Explore vulnerability checks for your environment with Hinoki.

Book a demo

Summary

What happened

Improper authentication in Webauthn Framework 3.3.0 through 3.3.3 allows remote attackers to log in without user presence. The framework fails to verify the user-present bit in signed WebAuthn assertions, allowing an attacker controlling the user's system to request an assertion from an attached FIDO2 authenticator without a physical button press or equivalent presence test. The attacker requires direct control of the user's system and authenticator access; successful use permits login to the relying service, with the record describing authentication bypass rather than independent data or service-impact capabilities.

The record

CVE
CVE-2021-38299
Published
Sep 27, 2021
Updated
Aug 4, 2024
Vendor
Unknown vendor
Product
Unknown product
Classifications
CWE-287, T1078
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Sep 27, 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

Compare your product and version with the public record. A matching version still requires validation against your environment.

Is a vulnerable build present?

Affected buildAffected product and version details are unavailable.

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

Affected products and versions are unavailable in this record.

Published CVSS scores

7.5NVDAV:N/AC:L/Au:N/C:P/I:P/A:P
9.8NVDCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
5.9FZICVSS:3.1/AV:L/AC:L/PR:N/UI:N/S:U/C:L/I:L/A:L

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)
Vectornetwork
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-287Improper Authentication
T1078Valid Accounts

Public exploit references

No public exploit references are available in this record.

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

Technologies

Your stack

See the directory against your own environment.

Your stack

Check the software in your environment

Book a demo to see how Hinoki identifies affected software and validates exploitability in your environment.

Book a demo