As a catastrophic security flaw, CVE-2026-104803 has severe implications, demanding immediate intervention.
Status: Deferred
Last updated: 🕜 13 Oct 2026, 13:30 UTC
Originally published on: 🕗 10 Oct 2026, 08:17 UTC
Time between publication and last update: 3 days
CVSS Release: version 3
security@wordfence.com
Secondary
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
CVE-2026-104803: The WPCOM Member plugin for WordPress is vulnerable to Authentication Bypass in all versions up to, and including, 1.7.27 via the `uuid` and `code` parameters of the social-login callback handler registered on the `init` hook. The vulnerability exists because the `login` function's social-login flow performs no nonce validation, no OAuth state verification, and no per-visitor namespace isolation in the session store, allowing an unauthenticated attacker to issue a crafted GET request that writes an attacker-named, attacker-valued entry into the global session namespace (bypassing the per-visitor prefix by prepending an underscore), then issue a second GET request triggering `weapp_new_user()` to read that forged entry and resolve the attacker-supplied `openid` value to a bound WordPress account before `wp_set_auth_cookie()` establishes a fully authenticated session. This makes it possible for unauthenticated attackers to log in as any WordPress user — including administrators — whose bound social provider identifier (openid/unionid) is known or discoverable. Successful exploitation requires that the target site has at least one social provider configured (which activates the vulnerable handler) and that the attacker knows or can enumerate the victim account's bound openid or unionid.
The exploitability of CVE-2026-104803 depends on two key factors: attack complexity (the level of effort required to execute an exploit) and privileges required (the access level an attacker needs).
With low attack complexity and no required privileges, CVE-2026-104803 is an easy target for cybercriminals. Organizations should prioritize immediate mitigation measures to prevent unauthorized access and data breaches.
A lower complexity and fewer privilege requirements make exploitation easier. Security teams should evaluate these aspects to determine the urgency of mitigation strategies, such as patch management and access control policies.
Attack Complexity (AC) measures the difficulty in executing an exploit. A high AC means that specific conditions must be met, making an attack more challenging, while a low AC means the vulnerability can be exploited with minimal effort.
Privileges Required (PR) determine the level of system access necessary for an attack. Vulnerabilities requiring no privileges are more accessible to attackers, whereas high privilege requirements limit exploitation to authorized users with elevated access.
Above is the CVSS Sub-score Breakdown for CVE-2026-104803, illustrating how Base, Impact, and Exploitability factors combine to form the overall severity rating. A higher sub-score typically indicates a more severe or easier-to-exploit vulnerability.
Below is the Impact Analysis for CVE-2026-104803, showing how Confidentiality, Integrity, and Availability might be affected if the vulnerability is exploited. Higher values usually signal greater potential damage.
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