CVE-2026-15341: User Session Synchronizer WordPress plugin authentication bypass (CVSS 9.8)

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 3.1 breakdown

Attack vectorNetwork

Attack complexityLow

Privileges requiredNone

User interactionNone

ScopeUnchanged

ConfidentialityHigh

IntegrityHigh

AvailabilityHigh

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H

Remediation

No fixed version is recorded in the NVD data. Check the vendor advisory for the latest guidance.

References

Related CVEs

Recent high-severity vulnerabilities sharing a weakness type.

Frequently asked

Is CVE-2026-15341 being actively exploited?

CVE-2026-15341 is not in the CISA KEV catalog. Its EPSS exploit probability is 0.58%.

How severe is CVE-2026-15341?

CVE-2026-15341 has a CVSS 3.1 base score of 9.8, rated critical. EPSS estimates a 0.58% probability of exploitation.

How do I fix CVE-2026-15341?

Apply the vendor's patch or advisory guidance, then verify no affected versions remain across your devices.

How Secuno handles this

Secuno correlates vulnerabilities like CVE-2026-15341 against the real software inventory on every managed device, as each hourly inventory arrives. Rather than a static severity, each match is scored in context: exploit availability, EPSS, the asset's exposure, and business criticality decide where it lands in the queue. If an affected version is present anywhere across your portfolio, it surfaces automatically with a prioritised remediation path.

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