CVE-2026-15341
User Session Synchronizer <= 1.4.0 - Unauthenticated Authentication Bypass to Account Takeover via 'ussync-key', 'ussync-token', and 'ussync-ref' Parameters
- Published
- Updated
- Reserved
- Assigned by
- Wordfence
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.
Timeline
ID reserved
By Wordfence
- 37 days later
· 37 days later
Published
- 2 days later
· 2 days later
Record updated
Changes after publication (a new score, a public exploit, EPSS crossing 1, 10 or 50 %, leaving KEV) are kept since November 2026; earlier ones are not known.
Scores
| Scored by | CVSS | Score | Vector |
|---|---|---|---|
| WordfenceCNA (assigner) | 3.1 | Critical9.8 | CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H |
| NVDNVD · Deferred | 3.1 | Critical9.8 | CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H |
- EPSS (exploitation in 30 days)
- 0.58% · top 52% of all CVEs (7 Nov 2026)
- CISA SSVC
- Exploitation: none · Automatable: yes · Technical impact: total
The list uses the assigner's score when there is one, then CISA's, then NVD's: Critical 9.8.
Weakness
Affected products
rafasashi · User Session Synchronizer
- affected ≤ 1.4.0
References (7)
- https://www.wordfence.com/threat-intel/vulnerabilities/id/cbc32e6d-47c5-4050-ba77-5a54203fe56a?source=cve (opens in a new tab)
- https://plugins.trac.wordpress.org/browser/user-session-synchronizer/tags/1.4.0/includes/class-user-session-synchronizer.php#L422 (opens in a new tab)
- https://plugins.trac.wordpress.org/browser/user-session-synchronizer/tags/1.4.0/includes/class-user-session-synchronizer.php#L117 (opens in a new tab)
- https://plugins.trac.wordpress.org/browser/user-session-synchronizer/tags/1.4.0/includes/class-user-session-synchronizer.php#L286 (opens in a new tab)
- https://plugins.trac.wordpress.org/browser/user-session-synchronizer/tags/1.4.0/includes/class-user-session-synchronizer.php#L310 (opens in a new tab)
- https://plugins.trac.wordpress.org/browser/user-session-synchronizer/tags/1.4.0/includes/class-user-session-synchronizer.php#L631 (opens in a new tab)
- https://plugins.trac.wordpress.org/browser/user-session-synchronizer/tags/1.4.0/includes/class-user-session-synchronizer.php#L598 (opens in a new tab)
Sources
The same CVE in the primary databases and aggregators, to check against.
- CVE.org record (opens in a new tab)
- CVE List JSON (GitHub) (opens in a new tab)
- NVD (opens in a new tab)
- FIRST EPSS (opens in a new tab)
- OSV.dev (opens in a new tab)
- GitHub Advisories (opens in a new tab)
- CIRCL Vulnerability-Lookup (opens in a new tab)
Badge for a README or a ticket
[](https://trackcve.app/cve/CVE-2026-15341)Record last updated .