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WPMU DEV Dashboard EUVDEUVD-2026-67464

| CVE-2026-76581 CRITICAL
Improper Verification of Cryptographic Signature (CWE-347)
2026-08-28 Wordfence GHSA-2cxw-5886-mfv5
9.8
CVSS 3.1 · Vendor: Wordfence
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Attack ChainAIDerived

Hypothetical attack flow derived from CVE metadata – not a confirmed exploit chain

  1. Recon
    Identify site with WPMU DEV Hub SSO
  2. Delivery
    Call unauthenticated wdpsso_step1 action
  3. Exploit
    Obtain valid HMAC over concatenated fields
  4. Install
    Move domain into redirect field
  5. C2
    Replay signature to wdpsso_step2
  6. Execute
    Receive authenticated administrator session
  7. Impact
    Full site takeover

Vulnerability Assessment

Weakness
CWE
OWASP Top 10:2025
A04:2025 - Cryptographic Failures
ASVS 5.0
V11 - Cryptography Signature verification
Exploitation Conditions

Exploitation requires the target WordPress site to be connected to WPMU DEV with the Hub SSO feature enabled and the SSO mapping pointed at an administrator account - this is the exact precondition stated in the description and is the primary factor limiting exploitation. Given the confirmed CVSS vector (PR:N/UI:N), no authentication and no user interaction are needed once that configuration is present: the attacker directly calls the unauthenticated wdpsso_step1 and wdpsso_step2 AJAX actions. Sites that have not enabled Hub SSO, are not connected to the Hub, or map SSO to a non-administrator are not exploitable, so this is not a default-configuration flaw despite the network-facing, unauthenticated attack surface.

Impact

The CVSS 3.1 vector (AV:N/AC:L/PR:N/UI:N, C:H/I:H/A:H, 9.8 Critical) indicates remote, unauthenticated, low-complexity exploitation with full compromise - consistent with an authentication bypass that yields an administrator session. No EPSS score, KEV entry, SSVC decision, or public POC was provided, so predicted exploitation probability is unknown and there is no evidence of active exploitation; the finding is a Wordfence threat-intel disclosure. The most important qualifier is that CVSS does not capture the deployment precondition: exploitation only works on sites actively connected to WPMU DEV with Hub SSO enabled and mapped to an administrator. This means the raw 9.8 overstates blanket risk - real risk is high specifically for that configured subset and materially lower for sites not using Hub SSO. Net: treat as a genuine critical for affected configurations, but scope exposure by checking whether Hub SSO is enabled before triaging site-wide panic.

Exploit ScenarioDerived

An attacker targeting a WordPress site that uses WPMU DEV Hub SSO calls the unauthenticated wdpsso_step1 AJAX action to obtain a validly HMAC-signed token that discloses the token, state, redirect, and domain values. They then replay that signature to wdpsso_step2 with the domain value moved into the redirect field, satisfying the verifier's three-field concatenation and receiving an authenticated administrator session. No public POC is noted, but low attack complexity and no authentication requirement make weaponization straightforward once the message-construction quirk is understood.

Act Now Prioritize within 24-48h. Why: CRITICAL severity.
No patch listed yet 0.3% exploitation probability (EPSS)

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AnalysisAIv1 – Aug 28, 2026

Authentication bypass in the WPMU DEV Dashboard WordPress plugin (all versions through 5.0.1) lets an unauthenticated attacker forge a valid administrator session by abusing an HMAC signature-verification flaw in the Hub SSO login flow. Because the signing routine in the unauthenticated wdpsso_step1 action covers a different, unseparated field concatenation than the verifier in wdpsso_step2, an attacker can obtain a legitimately signed token and replay it with fields rearranged to authenticate as admin. No public exploit is identified at time of analysis, but the network-reachable, unauthenticated nature and 9.8 CVSS make this a high-priority patch item.

RemediationAI

No vendor-released patch version is identified in the provided data; the description states all versions through 5.0.1 are vulnerable, which implies a fixed release above 5.0.1 but this could not be independently confirmed, so upgrade to the latest available WPMU DEV Dashboard release and monitor https://wpmudev.com/project/wpmu-dev-dashboard/ and the Wordfence advisory for the exact patched version. As an immediate compensating control, disable the Hub SSO feature in the WPMU DEV Dashboard (this removes the exploitable step1/step2 flow but also disables one-click Hub login for administrators), or disconnect the site from WPMU DEV Hub until patched. If SSO must remain enabled, restrict access to admin-ajax.php for the wdpsso_step1 and wdpsso_step2 actions at a WAF or reverse proxy, or ensure the mapped Hub user is not an administrator (trade-off: reduces the impact of a forged session but may break intended admin SSO workflows). Rotate WPMU DEV Hub connection credentials after patching in case tokens were previously disclosed.

Affected VersionsENISA

WPMU DEV Dashboard 0 ≤5.0.1

Affected Packages

euvd wpmu_dev_dashboard no fix

Source: OSV (Open Source Vulnerabilities)

Affects your stack

Affects 1 package in euvd

Checking this CVE against your own stacks and servers is part of the Basic plan and up.

Technical ContextAI · show details

The vulnerability lives in WordPress AJAX handlers (admin-ajax.php actions wdpsso_step1 and wdpsso_step2) that implement Single Sign-On between a WordPress site and the WPMU DEV Hub. The root cause is CWE-347 (Improper Verification of Cryptographic Signature): the HMAC is computed over a raw, unseparated concatenation of the token, state, redirect, and domain values. Because the fields are joined without a delimiter, and because step 1 signs four fields while step 2 verifies only three (omitting domain), the message boundaries are ambiguous. This canonicalization/message-construction weakness means two semantically different field arrangements produce the same HMAC input string, so a signature legitimately issued by step 1 validates against a maliciously reordered payload in step 2. The affected component is identified by CPE cpe:2.3:a:wpmudev:wpmu_dev_dashboard, all versions up to and including 5.0.1.

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Severity by source

Vendor (Wordfence) PRIMARY 9.8 CRITICAL
AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
vuln.today AI 9.8 CRITICAL

Unauthenticated network-reachable AJAX replay (PR:N/UI:N/AC:L) yielding a full administrator session gives C:H/I:H/A:H; the Hub SSO config precondition is a deployment scope factor not captured by 3.1 base metrics.

3.1 AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
4.0 AV:N/AC:L/AT:P/PR:N/UI:N/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N

Primary rating from Vendor (Wordfence).

CVSS VectorVendor: Wordfence

Attack Vector
Network
Attack Complexity
Low
Privileges Required
None
User Interaction
None
Scope
Unchanged
Confidentiality
High
Integrity
High
Availability
High

DescriptionCVE.org

The WPMU DEV Dashboard plugin for WordPress is vulnerable to Authentication Bypass in all versions up to, and including, 5.0.1. This is due to inconsistent and ambiguous HMAC message construction between the unauthenticated wdpsso_step1 and wdpsso_step2 AJAX actions, where step 1 signs and discloses an unseparated concatenation of the token, state, redirect, and domain values, while step 2 verifies an unseparated concatenation that omits the domain field. This makes it possible for unauthenticated attackers, on sites connected to WPMU DEV with Hub SSO enabled and mapped to an administrator, to obtain a valid HMAC from step 1 and replay it to step 2 by moving the domain value into the redirect field, resulting in an authenticated administrator session.

Executive ViewAI

Why It Matters

The WPMU DEV Dashboard WordPress plugin (versions through 5.0.1) contains a critical authentication bypass vulnerability that allows unauthenticated attackers to gain administrator access through HMAC signature verification flaws in the SSO login flow. Any organization using this plugin faces immediate risk of complete WordPress compromise, including data theft, malware injection, and account takeover. No vendor-released patch identified at time of analysis; organizations must implement immediate interim protective measures.

Business Impact: Severe
Compensating Controls

Disable the WPMU DEV Dashboard plugin immediately; restrict network access to WordPress installations via WAF rules blocking the SSO endpoints or IP whitelisting to administrative networks only; implement real-time monitoring and alerting for administrator account creation and privilege escalation attempts; maintain isolated backups of WordPress configuration and user databases for rapid recovery.

Threat Intelligence Overview

EPSS Score
0.3%
Top 74% exploitable
Prevalence
Medium
popular WPMU DEV membership plugin, but exploit needs Hub SSO enabled
Data Quality
5 sources
Confidence: Medium

How this decision was reached

The engine reads each signal below and applies a fixed list of rules from top to bottom. The first rule that matches sets the recommended action – like a statement, every line is shown.

SignalValue
Severity CRITICAL
CISA KEV No
Public POC No
EPSS 0.3%
Patch available No
Active threat No
Deciding rule
CRITICAL severity
What every action level means
Emergency Immediate action required. Criteria: CRITICAL + in CISA KEV (actively exploited) without patch, OR CRITICAL + EPSS > 30% without patch, OR CRITICAL + active threat signals without patch.
Act Now Prioritize within 24-48h. Criteria: in KEV with patch available, OR CRITICAL + public POC, OR HIGH + EPSS > 10%, OR CRITICAL + active threat, OR any CRITICAL severity.
This Week Schedule remediation this week. Criteria: HIGH severity (CVSS 7.0-8.9). Patch within normal change window.
This Month Plan within 30 days. Criteria: MEDIUM severity (CVSS 4.0-6.9), lower exploitation probability. Include in regular patch cycle.
Monitor Track and reassess. Criteria: LOW severity (CVSS 0.1-3.9), minimal exploitation risk. No immediate action needed.

SSVC AssessmentENISA

SSVC Decision
Out-of-Cycle
Exploitation
None
System Exposure· derived
Open
Automatable
Yes
Human Impact
Very High
Technical Impact
Total

Priority Score

49
Low Medium High Critical
KEV: 0
EPSS: 0
CVSS: +49
PoC: 0
Weaponized: 0
Threat intel: 0
Gov advisory: 0

Attack Technique

Authentication bypass attacks exploit flaws in the verification mechanisms that control access to systems and applications.

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