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CVE-2026-18439

CVE-2026-18439 — Tutor LMS <= 4.0.7 - Authenticated (Custom+) Insecure Direct Object Reference to Arbitrary Quiz Question/Answer Modification and Deletion via 'payload' Parameter

The Tutor LMS – eLearning and online course solution plugin for WordPress is vulnerable to Insecure Direct Object Reference in versions up to, and including, 4.0.7 via the tutor_quiz_builder_save AJAX action due to missing validation that nested question_id, answer_id, deleted_question_ids[], and deleted_answer_ids[] values in the submitted payload belong to a quiz/topic/course the requester is authorized to manage. The handler only validates the top-level course_id, topic_id, and (when supplied) payload['ID'], but the nested identifiers are passed straight into $wpdb->update/DELETE statements in QuizBuilder::save_questions(), QuizBuilder::save_question_answers(), and QuizBuilder::handle_delete(). This makes it possible for authenticated attackers, with Instructor-level access and above, to overwrite the content and re-parent arbitrary quiz questions/answers belonging to other instructors or administrators, and to delete arbitrary quiz question and answer rows.

Published Updated Sources: NVD, themeum (CNA), GitHub, GitHub Security Advisory, SOCRadar CTI

Triage

Is it exploited, how likely is exploitation, what does it touch, and how severe do the scoring sources call it.

Exploitation

Reported

not confirmed by CISA

EPSS

0%

ahead of 0% of scored CVEs

Affects

themeum

Tutor LMS – eLearning and online course solution

CVSS base

4.3

medium

Remediation

The vendor's own words where we have them.

Upgrade Tutor LMS – eLearning and online course solution to a fixed release. Apply vendor patches per advisory and restrict external exposure of the affected component until patched.

First 24 hours

Ordered from the record's own fields — exposure first, because you cannot patch what you have not found.

  • Identify exposed assets running affected vendor/product/version combinations.
  • Prioritize based on EPSS, PoC availability, and external exposure.
  • Search available logs for exploit probes, errors, authentication anomalies, or suspicious child processes matching the vulnerability class.

Affected scope

Vendor, product and version as the advisories word them.

VendorProductVersionsStatus
themeumTutor LMS – eLearning and online course solution0 to <= 4.0.7Vulnerable

Attack characteristics

The CVSS vector, decoded. It describes the attack, not your exposure to it.

Availability

None

Confidentiality

None

Integrity

Low

Scope

Unchanged

Attack Complexity

Low

Attack Vector

Network

Privileges Req

Low

User Interaction

None

Every base score collected

Sources score independently and disagree; each row says who scored it and under which version.

ScoreVersionSeverityExpl.ImpactSource
4.3CVSS 3.1medium2.81.4NVD, themeum (CNA), GHSA

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

What this weakness leads to

MITRE's own consequences and mitigations for the weakness class — the authority's wording, not guidance derived from the CVSS vector.

MITRE

CWE-639 · Authorization Bypass Through User-Controlled Key

  • Bypass Protection Mechanism
  • Gain Privileges or Assume Identity

Mitigation: For each and every data access, ensure that the user has sufficient privilege to access the record that is being requested.

Weakness & attack patterns

  • CWE-639

Inferred from the weakness class — not observed against this CVE.

CAPEC-1 · Accessing Functionality Not Properly Constrained by ACLsCAPEC-122 · Privilege Abuse

Public exploit

Capability, not use: code existing is a different claim from anyone running it.

Repositories

3

1 of the 3 sampled are weaponized

Detection

Read off the CVSS vector and the weakness class. Starting points, not rules we have tested.

  • Search application, proxy, and WAF logs for requests touching /topic/course, /DELETE, /answers.
  • Prioritize edge telemetry for network-reachable Tutor LMS – eLearning and online course solution.
  • Monitor for scanner or exploit-pattern traffic after 3 public PoC repositories were reported.
web/proxy/WAF logsapplication logsnetwork IDS/IPS

Timeline

What happened to this CVE, newest first — with the readings a source repeats on a schedule counted underneath rather than listed.

  1. 2026

  2. Added · CVSS 3.1 4.3 (AV:N)

    Sep 22, 2026 · NVD

  3. Initial · CVE published

    Sep 22, 2026 · NVD

  4. Added · GHSA-9x9f-f428-ff8p published (medium)

    Sep 22, 2026 · GitHub Security Advisory

  5. CVE published by MITRE.

    Sep 22, 2026 · SOCRadar CTI

  6. Reported · Disclosed

    Sep 21, 2026 · themeum

  7. Reported · Vendor Notified

    Jul 30, 2026 · themeum

Source activity

Readings a source repeats on a schedule, counted rather than listed.

  • 1×2 times mentioned on 1 Telegram channelsSep 22, 2026 · SOCRadar CTI

References

14 on the record

Elsewhere on this site

Not in any source we poll

Listed rather than left blank: an empty field and an unmeasured one look identical on screen, and only one is a reason to look elsewhere.

  • No confirmed IOCs, IP addresses, domains, file hashes, or malware artifacts supplied.
  • No organization-specific asset inventory, compensating-control status, or patch deployment evidence supplied.
  • No exploit packet captures, log samples, or incident case IDs supplied.
Answered from this record1

What should defenders know first?

CVE-2026-18439 is Tutor LMS <= 4.0.7 - Authenticated (Custom+) Insecure Direct Object Reference to Arbitrary Quiz Question/Answer Modification and Deletion via 'payload' Parameter, a medium vulnerability affecting Tutor LMS – eLearning and online course solution from themeum. The current evidence does not list it in CISA KEV, and the exploit status is: Exploitation is reported, but no independent confirmation is available in the sources we have. Public exploit evidence is: 3 public PoC repositories reported; 1 marked weaponized in current dataset. The affected-version evidence is listed in the key facts and affected products tables. Defenders should first verify whether exposed or business-critical assets run those versions, then apply vendor patches or mitigations, restrict reachable attack surface, and preserve logs for detection review. CVSS 4.3 describes technical severity, while EPSS 0% helps estimate near-term exploit likelihood; neither replaces asset context. Unknown fields should remain explicit in tickets, and threat actor, IOC, victimology, or payload claims should not be added unless a cited source supports them. Monitor CISA KEV, vendor advisories, NVD changes, public PoC repositories, and internal telemetry for update triggers.