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Fencer Intel
high 8.1

CVE-2026-76877 json

WPML Multilingual CMS <= 4.9.7 - Unauthenticated Authentication Bypass in Language-per-Domain SSO via 'wpml_sso_token_domain' Parameter

published 2d ago modified 18h ago also EUVD-2026-120823

cvss
8.1
version 3.1, CNA
cisa kev
Not listed
not in CISA's catalog
epss
0.3%
EPSS 0.3% chance of exploitation in 30 days, percentile 26%
public exploits
0
none known

Summary

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.

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Exploit prediction

0.33% chance of exploitation in the next 30 days, higher than 26% of all scored CVEs (FIRST EPSS, 2026-11-11).

CVSS scores

assigned by version score vector
CNA 3.1 8.1 CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:H

Affected products

  • WPML WPML Multilingual CMS

Classification

Weakness
Technology feeds

References

Sources

Fencer Intel keeps one entry per vulnerability: the CVE id wins, then GHSA, and records that alias each other are merged, except that two CVEs always keep separate entries. The same data is available as JSON.