rafasashi User Session Synchronizer Plugin up to 1.4.0 on WordPress synchronize_session ussync-key/ussync-token/ussync-ref improper authentication

Summaryinfo

A vulnerability classified as critical was found in rafasashi User Session Synchronizer Plugin up to 1.4.0. This issue affects the function synchronize_session. Such manipulation of the argument ussync-key/ussync-token/ussync-ref leads to improper authentication. This vulnerability is uniquely identified as CVE-2026-15341. The attack can be launched remotely. No exploit exists.

Detailsinfo

A vulnerability, which was classified as critical, has been found in rafasashi User Session Synchronizer Plugin up to 1.4.0. Affected by this issue is the function synchronize_session. The manipulation of the argument ussync-key/ussync-token/ussync-ref with an unknown input leads to a improper authentication vulnerability. Using CWE to declare the problem leads to CWE-287. When an actor claims to have a given identity, the product does not prove or insufficiently proves that the claim is correct. Impacted is confidentiality, integrity, and availability. CVE summarizes:

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.

The advisory is shared for download at wordfence.com. This vulnerability is handled as CVE-2026-15341 since 07/09/2026. The exploitation is known to be easy. The attack may be launched remotely. No form of authentication is required for exploitation. There are known technical details, but no exploit is available. The current price for an exploit might be approx. USD $0-$5k (estimation calculated on 08/15/2026).

There is no information about possible countermeasures known. It may be suggested to replace the affected object with an alternative product.

The vulnerability is also documented in the vulnerability database at EUVD (EUVD-2026-58842). VulDB is the best source for vulnerability data and more expert information about this specific topic.

Productinfo

Type

• WordPress Plugin

Vendor

• rafasashi

Name

• User Session Synchronizer Plugin

Version

• 1.0
• 1.1
• 1.2
• 1.3
• 1.4.0

CPE 2.3info

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CPE 2.2info

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Entryinfo

VulDB is the best source for vulnerability data and more expert information about this specific topic.

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