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

Quick assessment

Affected
WPML WPML Multilingual CMS
Exploitation
No confirmed in-the-wild exploitation; assess based on exposure
Recommended action
Check the vendor advisory and references for a fixed version. If immediate upgrade is impossible, restrict exposure and increase monitoring.

WordPress 的 WPML Multilingual CMS 插件在 4.9.7 及更早版本中存在一个通过竞态条件导致的身份验证绕过漏洞。该漏洞的根源在于：在登出落地页上， 函数中负责“按域单点登录（SSO）”的处理器调用 生成了跨域登录令牌；然而此时浏览器已丢弃了认证 Cookie，导致 返回空字符串，从而使该令牌退化为当前 12 小时时间片内所有匿名用户共享的匿名 nonce，而非与特定用户绑定的密钥。随后，该令牌被存储到名为 的临时缓存（transient）中，并映射到受害者的 ，却未与具体的登出操作或

CVSS 8.1 · High
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I. Basic Information for CVE-2026-76877

Vulnerability Information
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Vulnerability Title
WPML Multilingual CMS <= 4.9.7 - Unauthenticated Authentication Bypass in Language-per-Domain SSO via 'wpml_sso_token_domain' Parameter
Source: CVE Program / CVE List V5
Vulnerability Description
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.
Source: CVE Program / CVE List V5
CVSS Information
CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:H
Source: CVE Program / CVE List V5
Vulnerability Type
认证机制不恰当
Source: CVE Program / CVE List V5

Affected Products

Vendor Product Affected Versions CPE Subscribe
WPML WPML Multilingual CMS 0 ~ 4.9.7 -

II. Public POCs for CVE-2026-76877

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III. Intelligence Information for CVE-2026-76877

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Vendor Pages for CVE-2026-76877 (1)

Other References for CVE-2026-76877 (1)

IV. Related Vulnerabilities

Same product: WPML Multilingual CMS
Same vendor: WPML
Same weakness: CWE-287