User Session Synchronizer <= 1.4.0 - Unauthenticated Authentication Bypass to Account Takeover via 'ussync-key', 'ussync-token', and 'ussync-ref' Parameters
Summary
| CVE | CVE-2026-15341 |
|---|---|
| State | PUBLISHED |
| Assigner | Wordfence |
| Source Priority | CVE Program / NVD first with legacy fallback |
| Published | 2026-08-15 03:16:47 UTC |
| Updated | 2026-08-20 12:48:10 UTC |
| 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. |
Risk And Classification
Primary CVSS: v3.1 9.8 CRITICAL from [email protected]
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
EPSS: 0.003330000 probability, percentile 0.263660000 (date 2026-08-20)
Problem Types: CWE-287 | CWE-287 CWE-287 Improper Authentication
| Version | Source | Type | Score | Severity | Vector |
|---|---|---|---|---|---|
| 3.1 | [email protected] | Secondary | 9.8 | CRITICAL | CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H |
| 3.1 | CNA | DECLARED | 9.8 | CRITICAL | CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H |
CVSS v3.1 Breakdown
Attack Vector
NetworkAttack Complexity
LowPrivileges Required
NoneUser Interaction
NoneScope
UnchangedConfidentiality
HighIntegrity
HighAvailability
HighCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
Vendor Declared Affected Products
| Source | Vendor | Product | Version | Platforms |
|---|---|---|---|---|
| CNA | Rafasashi | User Session Synchronizer | affected 1.4.0 semver | Not specified |
References
| Reference | Source | Link | Tags |
|---|---|---|---|
| plugins.trac.wordpress.org/browser/user-session-synchronizer/tags/1.4.0/includes/class-u... | [email protected] | plugins.trac.wordpress.org | |
| plugins.trac.wordpress.org/browser/user-session-synchronizer/tags/1.4.0/includes/class-u... | [email protected] | plugins.trac.wordpress.org | |
| www.wordfence.com/threat-intel/vulnerabilities/id/cbc32e6d-47c5-4050-ba77-5a542... | [email protected] | www.wordfence.com | |
| plugins.trac.wordpress.org/browser/user-session-synchronizer/tags/1.4.0/includes/class-u... | [email protected] | plugins.trac.wordpress.org | |
| plugins.trac.wordpress.org/browser/user-session-synchronizer/tags/1.4.0/includes/class-u... | [email protected] | plugins.trac.wordpress.org | |
| plugins.trac.wordpress.org/browser/user-session-synchronizer/tags/1.4.0/includes/class-u... | [email protected] | plugins.trac.wordpress.org | |
| plugins.trac.wordpress.org/browser/user-session-synchronizer/tags/1.4.0/includes/class-u... | [email protected] | plugins.trac.wordpress.org | |
| CVE Program record | CVE.ORG | www.cve.org | canonical |
| NVD vulnerability detail | NVD | nvd.nist.gov | canonical, analysis |
Vendor Comments And Credit
Discovery Credit
CNA: Afan (en)
CNA: moonge (en)
Additional Advisory Data
| Source | Time | Event |
|---|---|---|
| CNA | 2026-08-14T14:02:18.000Z | Disclosed |
There are currently no legacy QID mappings associated with this CVE.