Summary
Craft CMS: Passkey login accepts replayed WebAuthn assertions
Craft CMS passkey login accepts WebAuthn requestOptions from the unauthenticated login request body and does not persist the updated credential counter returned by the WebAuthn assertion validator. A captured passkey login request body can therefore be replayed because the old challenge is accepted again, and the stored credential counter remains stale.
Craft CMS 5.10.3 and current 5.x HEAD accept PublicKeyCredentialRequestOptions from the unauthenticated users/login-with-passkey request body and do not persist the updated PublicKeyCredentialSource returned/mutated by web-auth/webauthn-lib after assertion validation.
As a result, a captured passkey login request body is not one-time-use. Reposting the same requestOptions and response can result in validation against the same stale credential counter and create another Craft session for that user. This weakens passkeys from a fresh, server-challenged authentication ceremony into a replayable bearer artifact if one successful assertion body is exposed.
Attack Scenario
- A victim successfully logs in with a passkey.
- The
POST /actions/users/login-with-passkeybody containingrequestOptionsandresponseis captured from an application/request log, debugging proxy, browser extension, compromised analytics layer, or another request-body disclosure point. - The attacker reposts the same body to
users/login-with-passkey. - Craft deserializes the attacker-supplied
requestOptions, so the old challenge remains accepted for validation. - The WebAuthn validator compares the assertion's
signCountagainst the stale stored credential counter. - Because Craft did not persist the updated credential source on the original login, the same stale stored counter is used again.
- The same captured assertion validates and Craft creates another authenticated session for the victim account.
This is exactly what WebAuthn's challenge and signature-counter lifecycle is meant to prevent: a successful assertion should be bound to a server-issued challenge and should update server-side credential state so it cannot be used again.
Impact
An attacker who obtains one successful passkey login request body can replay it to create additional authenticated Craft sessions for that user. This defeats WebAuthn’s intended one-time challenge and signature-counter replay protection, reducing a passkey assertion to a reusable bearer artifact if exposed through request logging, a debugging proxy, a compromised same-origin script layer, or another request-body disclosure path.
The impact is an account/session takeover of the affected passkey account after a single assertion body is captured. The issue is in Craft’s native passkey login flow and affects fresh Craft installations with passkeys enabled.
Affected versions
Security releases
Kodem intelligence
Severity tells you how bad this could be in the worst case. It does not tell you whether you are exposed. Exploitability and impact are functions of runtime truth: whether the vulnerable code is present, reachable, and actually executes in your application. A vulnerable package can sit in your dependency tree and never run.
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Frequently Asked Questions
- What is GHSA-WG23-69C2-GJC8? GHSA-WG23-69C2-GJC8 is a critical-severity security vulnerability in craftcms/cms (composer), affecting versions >= 5.0.0-RC1, < 5.10.5. It is fixed in 5.10.5.
- Which versions of craftcms/cms are affected by GHSA-WG23-69C2-GJC8? craftcms/cms (composer) versions >= 5.0.0-RC1, < 5.10.5 is affected.
- Is there a fix for GHSA-WG23-69C2-GJC8? Yes. GHSA-WG23-69C2-GJC8 is fixed in 5.10.5. Upgrade to this version or later.
- Is GHSA-WG23-69C2-GJC8 exploitable, and should I be worried? Whether GHSA-WG23-69C2-GJC8 is exploitable in your environment depends on whether the vulnerable code is present and reachable. A CVSS score is a worst-case rating; it does not account for your specific deployment, configuration, or usage patterns. Kodem, an Intelligent Application Security platform, uses runtime intelligence to show which vulnerabilities actually execute in production, so you can focus on the ones that represent real risk. Get a demo
- What actually determines whether GHSA-WG23-69C2-GJC8 is exploitable, and how bad it is? Exploitability and impact are not fixed properties of a CVE. They depend on runtime truth: whether the vulnerable code is present, reachable, and actually executes in your application. A high CVSS score on a dependency that never runs is not the same as real risk. Kodem, an Intelligent Application Security platform, uses runtime intelligence to reveal which vulnerabilities actually execute in production, so teams prioritize the ones that genuinely matter.
- How do I fix GHSA-WG23-69C2-GJC8? Upgrade
craftcms/cmsto 5.10.5 or later.