Summary
@hono/oauth-providers: OAuth state check fails open on omitted state, enabling login CSRF and forced account linking
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.
A victim's authenticated browser session is used to submit forged requests to an application that cannot distinguish them from legitimate ones. Typical impact: state-changing actions performed as the victim without their consent.
CVE-2026-81888 has a CVSS score of 5.4 (Medium). The vector is network-reachable, no privileges required, and user interaction required. A CVSS score reflects the worst-case severity of the vulnerability, not your specific exposure. Whether this affects your application depends on whether the vulnerable code is present and reachable in your environment. A fixed version is available (0.8.6); upgrading removes the vulnerable code path.
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.
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. Kodem's runtime-powered SCA identifies whether this CVE is reachable in your applications.
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Frequently Asked Questions
- What is CVE-2026-81888? CVE-2026-81888 is a medium-severity cross-site request forgery (CSRF) vulnerability in @hono/oauth-providers (npm), affecting versions < 0.8.6. It is fixed in 0.8.6. A victim's authenticated browser session is used to submit forged requests to an application that cannot distinguish them from legitimate ones.
- How severe is CVE-2026-81888? CVE-2026-81888 has a CVSS score of 5.4 (Medium). This score reflects the worst-case severity of the vulnerability, not your specific exposure. Whether it represents real risk in your environment depends on whether the vulnerable code is present and reachable.
- Which versions of @hono/oauth-providers are affected by CVE-2026-81888? @hono/oauth-providers (npm) versions < 0.8.6 is affected.
- Is there a fix for CVE-2026-81888? Yes. CVE-2026-81888 is fixed in 0.8.6. Upgrade to this version or later.
- Is CVE-2026-81888 exploitable, and should I be worried? Whether CVE-2026-81888 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 CVE-2026-81888 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 CVE-2026-81888? Upgrade
@hono/oauth-providersto 0.8.6 or later.