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Moodle EUVDEUVD-2026-89725

| CVE-2026-102586 MEDIUM
Cross-site Scripting (XSS) (CWE-79)
2026-09-30 fedora GHSA-rfv4-mv3r-qx66
6.1
CVSS 3.1 · NVD
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Attack ChainAIDerived

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

  1. Access
    Craft reset link with scripted username
  2. Delivery
    Phish victim into clicking link
  3. Exploit
    Reset page reflects unsanitized input
  4. Execution
    Script executes in victim browser
  5. Impact
    Steal session data or act as user

Vulnerability Assessment

Weakness
CWE
OWASP Top 10:2025
A05:2025 - Injection
ASVS 5.0
V1 - Encoding and Sanitization Output encoding, context-aware escaping
MITRE ATT&CK

2 techniques across 2 tactics: Initial Access, Execution

The technique list with ATT&CK links and the kill-chain view is part of the Basic plan and up.

Exploitation Conditions

Exploitation requires convincing an unauthenticated user to click a specially crafted password-reset link that injects script via the username field on Moodle's password reset page (UI:R). It is a reflected XSS, so no stored persistence or authentication is needed, but success is limited by the required user interaction (the victim must open the attacker-supplied link) and by browser/CSP protections that may block inline script. Impact is confined to the victim's browser session in the Moodle origin (S:U, C:L only) rather than server-side code execution. Affected versions are not specified in the provided data.

Impact

The CVSS 3.1 vector (AV:N/AC:L/PR:N/UI:R/S:U/C:L/I:N/A:N, base 4.3) describes a reflected cross-site scripting flaw reachable over the network without authentication but requiring victim interaction, with only limited confidentiality impact and no integrity or availability impact - consistent with a low-to-moderate severity reflected XSS rather than a server-compromise bug. No EPSS score, KEV listing, POC, or SSVC decision data was provided, so all exploitation-likelihood signals are absent; per the rules this is 'no public exploit identified at time of analysis.' The signals are internally consistent (network reflected XSS gated by UI:R), so there is no CVSS-vs-description conflict to flag. Overall this is a real but modest-priority issue: exploitation depends on social-engineering a victim into clicking a crafted password-reset link, which caps practical impact, though Moodle's very large install base broadens the potential target pool.

Exploit ScenarioDerived

An attacker crafts a malicious Moodle password-reset URL embedding a username value laced with script, then phishes an unauthenticated user into opening it. When the reset page renders the unsanitized username, the injected JavaScript executes in the victim's browser within the Moodle origin, enabling session-relevant data theft or UI manipulation. No public proof-of-concept exploit was identified at time of analysis.

This Month Plan within 30 days. Why: MEDIUM severity (CVSS 4.0-6.9).
No patch listed yet 0.3% exploitation probability (EPSS)

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AnalysisAIv1 – Sep 30, 2026

Reflected cross-site scripting (XSS) in Moodle's password reset page allows unauthenticated remote attackers to execute arbitrary script in a victim's browser by tricking them into opening a crafted password-reset link containing a malicious username. The flaw stems from insufficient sanitization of the username input and is assigned CVSS 4.3 (AV:N/AC:L/PR:N/UI:R/S:U/C:L/I:N/A:N). No public exploit code or active exploitation is known at the time of analysis; an upstream fix commit (MDL-88335) is referenced but a released patched version is not independently confirmed.

RemediationAI

Apply the upstream fix commit referenced as MDL-88335 (http://git.moodle.org/gw?p=moodle.git&a=search&h=HEAD&st=commit&s=MDL-88335) or upgrade to a patched Moodle release once a fixed version is announced; the provided data does not specify an exact patched version. Until a patch is applied, consider implementing a strict Content Security Policy (CSP) that disallows inline script execution to mitigate XSS, but be aware this can break legitimate Moodle functionality that relies on inline JavaScript. Additionally, ensure that all user-supplied input on the password reset page is properly escaped and validated. Monitor the Moodle security advisories and the Red Hat CVE page (https://access.redhat.com/security/cve/CVE-2026-102586) for an official patch release. Blocking access to the password reset page entirely is not a practical workaround as it would disrupt legitimate users.

Affects your stack

Find out whether the stacks and servers you run are on an affected version.

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

Technical ContextAI · show details

Moodle is a PHP-based learning management system. The flaw is a reflected cross-site scripting (XSS) vulnerability (CWE-79) in the password reset page, where the username parameter is not properly sanitized before being reflected back to the user. An attacker can craft a malicious link that, when clicked by a victim, injects arbitrary JavaScript into the victim's browser within the context of the Moodle origin. Because the script executes in the victim's session, it can be used to steal cookies, session tokens, or perform actions on behalf of the user, but the CVSS vector (S:U, C:L) indicates the impact is limited to confidentiality within the browser and does not extend to server-side compromise. The attack requires user interaction (UI:R) to succeed, and no authentication is needed (PR:N). The fix is tracked in Moodle's git repository as MDL-88335, and Red Hat is also tracking the issue.

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Severity by source

Vendor (fedora) PRIMARY MEDIUM
NVD 6.1 MEDIUM
AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N
vuln.today AI 4.3 MEDIUM

Network-reachable reflected XSS needing no auth (PR:N) but a victim click (UI:R); limited in-origin confidentiality impact only, no integrity/availability, scope unchanged.

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

Primary rating from Vendor (fedora).

CVSS VectorNVD

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

Lifecycle Timeline

2
CVSS changed
Oct 01, 2026 - 15:52 NVD
4.3 (MEDIUM) 6.1 (MEDIUM)
CVE Published
Sep 30, 2026 - 08:36 cve.org
MEDIUM 4.3

DescriptionNVD

A flaw was found in Moodle. Insufficient sanitization of username input on the password reset page allows a remote attacker to conduct a cross-site scripting (XSS) attack. By convincing an unauthenticated user to access a specially crafted password reset link, an attacker could execute arbitrary script in the victim's browser.

Threat Intelligence Overview

EPSS Score
0.3%
Top 81% exploitable
Prevalence
High
Moodle is one of the most widely deployed open-source LMS platforms globally
Data Quality
6 sources
Confidence: High

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 MEDIUM
CISA KEV No
Public POC No
EPSS 0.3%
Patch available No
Active threat No
Deciding rule
MEDIUM severity (CVSS 4.0-6.9)
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· derived
Scheduled
Exploitation
None
System Exposure· derived
Open
Automatable
No
Human Impact· derived
High
Technical Impact
Partial

Priority Score

30
Low Medium High Critical
KEV: 0
EPSS: 0
CVSS: +30
PoC: 0
Weaponized: 0
Threat intel: 0
Gov advisory: 0

Attack Technique

Cross-Site Scripting occurs when an application accepts untrusted data and sends it to a web browser without proper validation or encoding.

Affected Products (CPE)NVD

cpe:2.3:a:moodle:moodle:*:*:*:*:*:*:*:*
cpe:2.3:a:moodle:moodle:*:*:*:*:*:*:*:*
cpe:2.3:a:moodle:moodle:*:*:*:*:*:*:*:*
cpe:2.3:a:moodle:moodle:*:*:*:*:*:*:*:*

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