Machine-written summary
Summary written by Claude Haiku from the source advisory. Not reviewed by a person.
The web-auth/webauthn-lib and web-auth/webauthn-framework PHP packages, versions 4.5.0 up to but not including 4.9.0, can reveal whether a username exists. When a username is not found, the assertion options returned by the ProfileBasedRequestOptionsBuilder method omit the allowedCredentials property, while valid usernames receive it, so an unauthenticated attacker who sends username requests to the assertion options endpoint can tell valid and invalid usernames apart. The source does not describe the exact fix in detail. Upgrade both packages to version 4.9.0 or later.
Not analysed yet
We haven’t published our analysis of this Advisory yet. Once a person has reviewed it, this page will say what’s vulnerable, what has to be true for your app to be affected, and how to check.
Severity and exploitation
| Score | Rating | CVSS | Vector | Source |
|---|---|---|---|---|
| 5.3 | Medium | 3.1 | CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:N/A:N | CNA (GitHub_M) |
- CISA KEV Not listed.
- EPSS 0.0039, the 33rd percentile, on 7 Nov 2026: FIRST’s estimate of the chance of exploitation in the next 30 days.
Timeline
- 31 Oct 2026, 14:03 UTC First seen by agentprime
- 31 Oct 2026, 14:03 UTC Confirmed by OSV
Sources
- GitHub Advisory Database: GHSA-875x-g8p7-5w27
- OSV: GHSA-875x-g8p7-5w27
- github.com/web-auth/webauthn-framework/security/advisories/GHSA-875x-g8p7-5w27
- nvd.nist.gov/vuln/detail/CVE-2024-39912
- github.com/web-auth/webauthn-framework/commit/64de11f6cddc71e56c76e0cc4573bf94d02be045
- github.com/web-auth/webauthn-framework/commit/a9d1352897fba552e659e1445a771dec2d4ed05a
- github.com/web-auth/webauthn-lib/commit/b6798de27cdedd8681fe4c9b13ace0ff2456d18b
- github.com/web-auth/webauthn-framework