CVE-2026-15341 Auth bypass in User Session Synchronizer
Unauthenticated attackers can bypass authentication and take over any user account, including administrators, by exploiting weak cryptographic validation in the User Session Synchronizer plugin.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Over the internet
- Victim action needed
- Not needed
- Fix
- None listed
What is CVE-2026-15341?
CVE-2026-15341 is a critical authentication bypass vulnerability in rafasashi User Session Synchronizer, published on 15 Aug 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.
Official 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.
Weakness: CWE-287
Which versions are affected by CVE-2026-15341?
How do I fix CVE-2026-15341?
No fix has been published for CVE-2026-15341 yet. Limit exposure of the affected software until one is available.
Upgrade, and rotate credentials and sessions that may have been exposed. More about Authentication bypass.
Is CVE-2026-15341 being exploited?
There is no known exploitation of CVE-2026-15341 in the wild and no public exploit code.
Sources
Also known as GHSA-r26j-82cg-5h6c.