Security readout for executives and security teams
Plain-English summary
CVE-2021-4416 affects the WordPress wp-mpdf plugin. A malicious site or link could cause a logged-in administrator's browser to submit unwanted post data because an admin save function did not properly validate a nonce. The business impact is limited integrity risk, not data theft or service outage based on the supplied CVSS vector.
Executive priority
Treat this as a moderate-priority WordPress hygiene issue. It does not indicate direct server takeover, data exposure, or active exploitation in the provided sources, but it can allow unwanted content changes if an administrator is socially engineered. Prioritize internet-facing WordPress sites and high-value publishing environments.
Technical view
The issue is CWE-352 CSRF in wp-mpdf through version 3.5.1, tied to missing or incorrect nonce validation in mpdf_admin_savepost(). The attack requires user interaction by an authenticated administrator, but no attacker authentication. The supplied references include a WordPress.org changeset, but the bundle does not provide detailed release guidance beyond the affected version statement.
Likely exposure
Exposure is likely limited to WordPress sites running wp-mpdf up to and including 3.5.1. Sites without the plugin, or with a vendor-confirmed fixed version, are not indicated as exposed. The affected-product metadata in the bundle appears incomplete, so confirm installed plugin name and version directly.
Exploitation context
The CVE is not listed as KEV, and the supplied sources do not show active exploitation. Abuse depends on tricking a logged-in site administrator into taking an action such as clicking a crafted link. This makes broad automated compromise less likely, but targeted administrator phishing remains plausible.
Researcher notes
The key technical claim is CSRF in mpdf_admin_savepost() from missing or incorrect nonce validation. The CVSS vector is AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:L/A:N. The source bundle says wp-mpdf <=3.5.1, but its structured affected entry is sparse, so version validation should rely on plugin inventory and vendor references.
Mitigation direction
- Inventory WordPress sites for wp-mpdf and record installed versions.
- Update wp-mpdf according to WordPress.org or vendor guidance.
- Disable or remove wp-mpdf where it is unused or cannot be updated.
- Reinforce administrator phishing controls and avoid untrusted links while authenticated.
- Review the referenced WordPress.org changeset for nonce-validation remediation context.
Validation and detection
- Confirm whether wp-mpdf is installed on each WordPress site.
- Verify installed versions are not up to and including 3.5.1.
- Check the admin save workflow includes valid nonce verification.
- Review logs for unexpected post changes by administrators after suspicious referrals.
- Confirm compensating controls if a fixed plugin version is unavailable.
Public sources used
Generated from the cited source records. This long-tail analysis has not been individually reviewed by a named human.
Conservative CVE-to-ATT&CK context
These mappings and lookup hints may be relevant to the vulnerability behavior, CWE, affected product, or exposure path. Glexia-inferred context is not an official MITRE, ATT&CK, CWE, or CVE Program mapping.
ATT&CK lookup starting points
Use these exact CWE pages and searches to review the Glexia ATT&CK library from this CVE's weakness and description context.
CWE-352: User-session and phishing behavior lookup
Client-side and session-facing weaknesses should be reviewed alongside initial-access and user-execution behaviors. Open the exact CWE lookup page first, then review the ATT&CK searches from that MITRE weakness context. This is a Glexia lookup hint, not an official ATT&CK mapping.
Open ATT&CK lookupCVE-2021-4416 mapping review
Open the CVE-to-ATT&CK bridge for reviewed, inferred, or future official mappings tied to this CVE.
Open ATT&CK lookup- Severity
- Medium
- CVSS
- 4.3 (3.1)
- Known Exploited
- No
- Published
Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:L/A:N
CNA and ADP enrichment extracted from CVE v5
These fields come from the CVE record and ADP containers, not from Glexia's Take. They preserve time-varying source decisions such as CISA SSVC, KEV status, CVSS metrics, and provider references.
CVSS vector scores
1 official scoreWe collect every scored CVSS vector available in the official CNA and ADP containers. When more than one version is present, the table keeps the source vectors side by side instead of collapsing them into the highest score.
CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:L/A:N2.81.4Primary CVE scoreVulnerability scoring details
Base CVSS 3.1 score
4.3MediumVector: CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:L/A:N
Source materials
- CVE List V5 sourceCVE List V5
- https://www.wordfence.com/threat-intel/vulnerabilities/id/c47386ee-25c8-4a77-92e8-5a82afc9c826?source=cveCVE reference
- https://blog.nintechnet.com/25-wordpress-plugins-vulnerable-to-csrf-attacks/CVE reference
- https://blog.nintechnet.com/more-wordpress-plugins-and-themes-vulnerable-to-csrf-attacks/CVE reference
- https://blog.nintechnet.com/multiple-wordpress-plugins-fixed-csrf-vulnerabilities-part-3/CVE reference
- https://blog.nintechnet.com/multiple-wordpress-plugins-fixed-csrf-vulnerabilities-part-2/CVE reference
- https://blog.nintechnet.com/multiple-wordpress-plugins-fixed-csrf-vulnerabilities-part-1/CVE reference
- https://blog.nintechnet.com/multiple-wordpress-plugins-fixed-csrf-vulnerabilities-part-5/CVE reference
- https://blog.nintechnet.com/multiple-wordpress-plugins-fixed-csrf-vulnerabilities-part-4/CVE reference
- https://plugins.trac.wordpress.org/changeset/2549363/wp-mpdf/trunk/wp-mpdf.phpCVE reference
Products and packages named in the record
CWE details
CWE links open Glexia weakness intelligence pages with official CWE context, developer remediation guidance, and related CVE mappings.
Cross-Site Request Forgery (CSRF)
Cross-Site Request Forgery (CSRF) represents a recurring weakness pattern that can create exploitable paths when design, validation, or implementation controls are missing.