@hono/oauth-providers: OAuth state check fails open on omitted state, enabling login CSRF and forced account linking

Exploitation

No confirmed exploitation recorded. Patch Next marks exploitation only from CISA KEV.

CVSS

5.4 · CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:L/I:L/A:N

EPSS

• CVE-2026-81888: 0.19% estimated exploitation activity in the next 30 days; percentile 8.88 (FIRST EPSS, 2026-11-03). This is a model estimate, not proof of exploitation or customer exposure.

As published by the source; long descriptions are shortened.

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…

Published by the source

31 Aug 2026, 20:30 UTC

Last modified by the source

31 Aug 2026, 20:30 UTC

Source last checked

26 Oct 2026, 13:01 UTC

1. Revision 1 · created · 26 Oct 2026

   Published from ghsa record GHSA-fm3f-ch8h-qw8q

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# Patch Next advisory brief: CVE-2026-81888

Advisory: @hono/oauth-providers: OAuth state check fails open on omitted state, enabling login CSRF and forced account linking
IDs: CVE-2026-81888, GHSA-fm3f-ch8h-qw8q
Record: https://patchnext.com/advisories/cve-2026-81888 (revision 1, source checked 26 Oct 2026, 13:01 UTC)
Inventory: none attached. This brief comes from a public page and does not say whether any deployment is affected.
Severity: Medium (CVSS 5.4)
Exploitation: no confirmed exploitation recorded. Patch Next confirms exploitation only from CISA KEV.
Vendor response: Vendor fix available; fixed versions by package: @hono/oauth-providers 0.8.6. A vendor fix does not mean a deployment is fixed.

## Affected components
- npm @hono/oauth-providers: affected < 0.8.6; fixed in 0.8.6

## Suggested inspection (read-only)
- `npm ls @hono/oauth-providers --all`: lists every installed copy and version, including transitive ones. Run in the project root after `npm ci`.

## Supported action
Upgrade each affected component to a fixed version on its release line. For a transitive dependency, upgrade the parent package or add an override or constraint, then regenerate the lockfile. Redeploy every environment that ran an affected version.

## Required regression checks
- Run the test suite and a production build.
- Exercise the features that depend on @hono/oauth-providers.
- Repeat the inspection and confirm that only fixed versions remain installed.

## Rollback considerations
- Keep the previous lockfile and deployment artifact. Rolling back reinstates the vulnerable version, so apply any documented mitigation while you fix forward.

## Unresolved questions
- Which deployments run an affected version?
- Exploitation status can change. Check again before lowering the priority.
- Mark the work resolved only after the fixed version is verified in production.

## Sources
- Verified: https://github.com/advisories/GHSA-fm3f-ch8h-qw8q (GitHub-reviewed advisory GHSA-fm3f-ch8h-qw8q lists affected ranges: npm @hono/oauth-providers >=0 <0.8.6)

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