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VulnerabilityPublished

web-auth/webauthn-lib · Webauthn lib: Webauthn: SimpleFakeCredentialGenerator with an empty secret produces predictable fake credentials, weakening username enumeration protection

Affects web-auth/webauthn-libSource GCVE Database

0

Public exploit available · CVSS 6.3 Medium : upgrade to 5.3.5 as a priority.

Data as of 8 Jul 2026, 13:41 UTC

CVSS 4.0 base score
6.3Medium
How severe the flaw is on the 0–10 CVSS scale.
Patch
Available – fixed in 5.3.5
CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:L/VI:N/VA:N/SC:N/SI:N/SA:N/E:P

What to do

Upgrade web-auth/webauthn-lib to 5.3.5.

Affected software

ProductAffectedFixed in
Packagistweb-auth/webauthn-libAffected
  • >=4.9.0 <5.3.5
Fixed in
  • 5.3.5

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AI-suggested

A fix is available in version 5.3.5 of web-auth/webauthn-lib. Users should upgrade to 5.3.5 or later. Until then, ensure that SimpleFakeCredentialGenerator is constructed with a non-empty, deployment-specific secret (e.g., the application secret). The Symfony bundle is not affected by default as it injects a non-empty secret. The library emits deprecation warnings when constructed without a secret to help detect misconfigurations. Providing a custom FakeCredentialGenerator implementation seeded with a secret is also a valid workaround.

Description

The Webauthn library's SimpleFakeCredentialGenerator, when instantiated without a secret, produces predictable fake credentials based solely on the username. This predictability allows attackers to distinguish between real and fake usernames, defeating the intended username enumeration protection. The issue affects versions from 4.9.0 up to but not including 5.3.5. The default Symfony bundle configuration is not affected as it injects a non-empty secret. The vulnerability is considered low severity since it only re-enables username enumeration and does not affect the validity of responses.

References

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