# CVE-2026-76877: WPML Multilingual CMS <= 4.9.7 - Unauthenticated Authentication Bypass in Language-per-Domain SSO via 'wpml_sso_token_domain' Parameter

Status: published. Published: 2026-11-10. Updated: 2026-11-10.

The WPML Multilingual CMS plugin for WordPress is vulnerable to Authentication Bypass via Race Condition in versions up to, and including, 4.9.7. This is due to the `process_iframe_request` function's language-per-domain SSO handler generating the cross-domain sign-in token via `wp_create_nonce('wpml_sso')` on the logout landing page, where the browser has already discarded its authentication cookies — so `wp_get_session_token()` returns an empty string and the token collapses to the shared anonymous nonce for the current 12-hour tick rather than a user-bound secret — and then storing it in the `wpml_sso_user_<token>_<sha256('wpml_sso'.$domain)>` transient mapped to the victim's `user_id` with no binding to the specific sign-out action or requesting client. Because an unauthenticated attacker can independently derive the identical token by triggering the logout confirmation flow on `wp-login.php?action=logout`, and because the `is_iframe_request()` gate conditions (the per-domain SSO `started` transient and domain-hash derived from the public constant `SSO_NONCE`) are fully computable within the 60-second `SSO_TIMEOUT` window, an unauthenticated attacker can submit the forged `wpml_sso_token_domain` parameter with a `wpml_user_signed_in` status to a secondary language-domain endpoint before the legitimate `wpml_user_signed_out` iframe fires, causing WordPress authentication cookies to be issued for the victim. This makes it possible for unauthenticated attackers to gain access to accounts of users — including administrators — who are actively in the process of logging out during the race window.

## Remediation

No remediation reported in collected sources

## Affected products and versions

- WPML / WPML Multilingual CMS: ≥ 0; ≤ 4.9.7 (affected, semver). Source: CNA: Wordfence

## Severity and prioritization

- CVSS 3.1: 8.1 (high); CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:H; source: CNA: Wordfence

- CISA KEV: No listing in collected sources

- EPSS: Not available

- SSVC: Not available

- Weaknesses: CWE-287

## Exploit evidence

No exploit evidence in collected sources. This is not proof of no exploitation.

## References

- https://www.wordfence.com/threat-intel/vulnerabilities/id/006d1fcd-77b4-4214-be71-b6d71afad072?source=cve (CNA: Wordfence)

- https://wpml.org/ (CNA: Wordfence)

## Provenance

- CNA: Wordfence: https://www.cve.org/CVERecord?id=CVE-2026-76877; retrieved 2026-11-10; source updated 2026-11-10

Revision: 0ee2acf3935e159ea081f251a429a729ab239821a5a904a7bbe6185aa9e5a481

Canonical: https://y2.dev/cve/CVE-2026-76877

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