CVE-2026-81888 is a medium-severity (CVSS 5.4) Cross-Site Request Forgery (CSRF) vulnerability in @hono/oauth-providers. A fix is available for @hono/oauth-providers — see the affected versions and patch details below.
@hono/oauth-providers: OAuth state check fails open on omitted state, enabling login CSRF and forced account linking
Exploitation Status
No confirmed exploitation observed yet
- CISA’s own triage has not observed active exploitation or public proof-of-concept code for this CVE as of its last assessment.
Exploitation and automatability from CISA’s SSVC triage for CVE-2026-81888.
EPSS Exploitation Probability
Probability of exploitation in the next 30 days, from FIRST.org EPSS.
How urgent is this, really
CVE-2026-81888 by exploitation likelihood (EPSS) against impact (CVSS). Outside the shaded patch-first corner.
Where this sits among everything scored
Of 390,400 CVEs with a current EPSS score, this one falls in the < 10% band (highlighted). Counts from FIRST.org, log-scaled.
Real-World Exposure
How broadly this vulnerability is actually deployed: weekly install volume shows current usage, and reverse-dependency count shows how many other packages break if it stays unpatched.
@hono/oauth-providersnpmDescription
Summary
The built-in social login providers accept an OAuth callback even when the state value is absent on both sides, so the anti-CSRF check passes for a callback that never came from a genuine login attempt. This defeats the state-based CSRF protection under default usage.
Details
The state check treated two absent values as a match, so a callback that omits state — and for which no state was ever stored — was allowed to redeem the authorization code. Hono's csrf() middleware does not help: it only inspects form-style requests, while the OAuth callback is a top-level GET navigation it treats as safe.
This affects the google, github, facebook, discord, twitch, linkedin, and msentra providers. The x (Twitter) provider is not exploitable due to its PKCE binding.
Impact
An attacker can make a victim's browser complete an OAuth callback that binds the attacker's identity instead of the victim's, leading to login CSRF (the victim silently acts inside the attacker's account) or forced account linking (the attacker's identity is linked to the victim's account, enabling later sign-in as the victim). Affects applications using an affected provider on @hono/oauth-providers 0.8.5 or earlier.
Affected Packages
| Ecosystem | Package | Vulnerable range | Fix |
|---|---|---|---|
| 📦npm | @hono/oauth-providers | all versions | 0.8.6npm install @hono/oauth-providers@0.8.6 |
Detection & mitigation playbook
Open-source dependencyDetect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for @hono/oauth-providers, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.
Fix
Update @hono/oauth-providers to 0.8.6 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2026-81888 is resolved across your whole dependency graph.
Workarounds
If you can't upgrade right away: gate or disable the affected feature, validate untrusted input at the boundary, and avoid passing attacker-controlled data into the vulnerable path. O3's runtime protection blocks exploitation in production as an interim safeguard until the upgrade lands.
Frequently Asked Questions
Is CVE-2026-81888 in your dependencies?
Find it across npm, including transitive dependencies.