CVE-2026-15341: CWE-287 Improper Authentication in rafasashi User Session Synchronizer
The User Session Synchronizer plugin for WordPress is vulnerable to Authentication Bypass leading to Account Takeover in all versions up to, and including, 1.4.0. The `synchronize_session()` function, hooked on `init` and therefore executed on every request, performs no nonce, capability, or shared-secret validation against the attacker-supplied `ussync-key`, `ussync-token`, and `ussync-ref` parameters; when `ussync-key` references an unregistered slot, `get_option()` returns `false` for both the secret key and the domain list, causing the AES-256-CBC encryption key to degrade to the fully predictable `md5('')` and the referer allowlist to collapse to an empty-string match, while the AES IV is unconditionally hard-coded as `md5('another-secret')`. This makes it possible for unauthenticated attackers to supply a crafted request encrypting any known or guessable user email address in the `ussync-ref` parameter, causing the handler to call `wp_set_auth_cookie()` for the matched user and granting full authentication as that user — including administrators — with no prior knowledge of site secrets.
AI Analysis
Technical Summary
CVE-2026-15341 is an authentication bypass vulnerability in the User Session Synchronizer WordPress plugin by rafasashi, affecting all versions up to and including 1.4.0. The vulnerability arises from the synchronize_session() function, which executes on every request without validating nonce, capability, or shared-secret parameters. When an attacker supplies an unregistered ussync-key, the encryption key degrades to a predictable value (md5('')), and the referer allowlist becomes ineffective. The AES IV is hard-coded as md5('another-secret'). This allows attackers to craft requests that encrypt known or guessable user email addresses in the ussync-ref parameter, causing the plugin to call wp_set_auth_cookie() and authenticate the attacker as the targeted user without prior knowledge of site secrets.
Potential Impact
Successful exploitation grants full authentication as any user, including administrators, leading to complete account takeover. This compromises confidentiality, integrity, and availability of the affected WordPress site, allowing attackers to perform any actions permitted to the compromised user.
Mitigation Recommendations
Patch status is not yet confirmed — check the vendor advisory for current remediation guidance. Until an official fix is available, users should consider disabling the User Session Synchronizer plugin or restricting access to it. Monitor vendor channels for updates and apply patches promptly once released.
CVE-2026-15341: CWE-287 Improper Authentication in rafasashi User Session Synchronizer
Description
The User Session Synchronizer plugin for WordPress is vulnerable to Authentication Bypass leading to Account Takeover in all versions up to, and including, 1.4.0. The `synchronize_session()` function, hooked on `init` and therefore executed on every request, performs no nonce, capability, or shared-secret validation against the attacker-supplied `ussync-key`, `ussync-token`, and `ussync-ref` parameters; when `ussync-key` references an unregistered slot, `get_option()` returns `false` for both the secret key and the domain list, causing the AES-256-CBC encryption key to degrade to the fully predictable `md5('')` and the referer allowlist to collapse to an empty-string match, while the AES IV is unconditionally hard-coded as `md5('another-secret')`. This makes it possible for unauthenticated attackers to supply a crafted request encrypting any known or guessable user email address in the `ussync-ref` parameter, causing the handler to call `wp_set_auth_cookie()` for the matched user and granting full authentication as that user — including administrators — with no prior knowledge of site secrets.
CVSS v3.1
Score 9.8critical
Affected software
rafasashi
User Session Synchronizer
Weaknesses
AI-Powered Analysis
Machine-generated threat intelligence
Technical Analysis
CVE-2026-15341 is an authentication bypass vulnerability in the User Session Synchronizer WordPress plugin by rafasashi, affecting all versions up to and including 1.4.0. The vulnerability arises from the synchronize_session() function, which executes on every request without validating nonce, capability, or shared-secret parameters. When an attacker supplies an unregistered ussync-key, the encryption key degrades to a predictable value (md5('')), and the referer allowlist becomes ineffective. The AES IV is hard-coded as md5('another-secret'). This allows attackers to craft requests that encrypt known or guessable user email addresses in the ussync-ref parameter, causing the plugin to call wp_set_auth_cookie() and authenticate the attacker as the targeted user without prior knowledge of site secrets.
Potential Impact
Successful exploitation grants full authentication as any user, including administrators, leading to complete account takeover. This compromises confidentiality, integrity, and availability of the affected WordPress site, allowing attackers to perform any actions permitted to the compromised user.
Mitigation Recommendations
Patch status is not yet confirmed — check the vendor advisory for current remediation guidance. Until an official fix is available, users should consider disabling the User Session Synchronizer plugin or restricting access to it. Monitor vendor channels for updates and apply patches promptly once released.
Technical Details
- Data Version
- 5.2
- Assigner Short Name
- Wordfence
- Date Reserved
- 2026-07-09T20:00:20.994Z
- Cvss Version
- 3.1
- State
- PUBLISHED
Threat ID: 6a7fd216bf8831d53949a64e
Added to database: 08/15/2026, 02:42:30 UTC
Last enriched: 08/22/2026, 13:21:43 UTC
Last updated: 09/28/2026, 01:47:41 UTC
Views: 113
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