vulnerability / NVI-00006287 / Revision 1
Webauthn: SimpleFakeCredentialGenerator with an empty secret produces predictable fake credentials, weakening username enumeration protection
OSV carries this publisher advisory for web-auth/webauthn-lib. This is an aggregated source copy; consult the original publisher and compare update dates.
This report has not inspected your inventory, configuration, deployed build, reachability or evidence. A catalog listing and a severity score do not establish exposure or compromise.
01 / Meaning
Why it matters
Published affected context helps an owner decide what evidence to gather. This report has not examined your application.
02 / Applicability
The affected context
Affected versions, configuration prerequisites and known exclusions are public. Confirm each one against the deployed service.
web-auth/webauthn-lib
source listedECOSYSTEM: introduced 4.9.0; fixed 5.3.5
## Impact `Webauthn\SimpleFakeCredentialGenerator` is the library-provided default implementation of the `FakeCredentialGenerator` interface. It returns a stable list of decoy `PublicKeyCredentialDescriptor` objects for a given username so that an assertion request for an unknown user looks the same as a request for a real one, which mitigates username enumeration. The generator derives the whole decoy list from a single seed: ```php $seed = hash('sha256', $username . $this->secret, true); ``` When it is constructed without a secret (its constructor default, `$secret = ''`), the seed depends only on the username. The username is attacker-chosen and the algorithm is public, so an unauthenticated requester can recompute the exact, byte-for-byte decoy list the server returns for any username. The attacker then compares a probed username's response against the locally computed list and decides whether the account is real or fake, which is precisely the distinction the mechanism is meant to hide. With any non-empty secret the seed becomes a value the attacker cannot evaluate and the mitigation holds. The defect is the empty default, not the algorithm. ## Affected configurations -
03 / Response
What to do next
- vendor patch
The original advisory lists fixed boundaries 5.3.5 for web-auth/webauthn-lib. Confirm the publisher’s latest guidance.
Confirm current vendor support, compatibility and deployment evidence. This report has not tested a fix in your system. GitHub Advisory Database via OSV
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04 / Limits
What this report cannot establish
- Customer inventory, deployment, reachability and exploitation have not been inspected.
05 / Provenance
Sources you can inspect
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- GHSA-gq4g-fpc9-vjfq ↗
GitHub Advisory Database via OSV · vendor advisory
Observed . GitHub-origin advisory, CC-BY-4.0; OSV is an aggregate copy, not independent corroboration.
Public revision history
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- Revision 1 ·
First indexed by Null; source disclosure date is shown separately.