CVE-2021-47857

Moodle 3.10.3 contains a persistent cross-site scripting vulnerability in the calendar event subtitle field that allows attackers to inject malicious scripts. Attackers can craft a calendar event with malicious JavaScript in the subtitle track label to execute arbitrary code when users view the event.

CVSS 5.1 · Medium

External lookup

Potential internet exposure

Potential exposure only — not proof of vulnerability.Shodan results indicate potentially internet-exposed products, not confirmed vulnerable systems. They do not confirm that any returned system is vulnerable to CVE-2021-47857.

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Product CPE queries

Derived from this CVE's existing NVD CPE 2.3 records; the application, operating-system, or hardware part is retained.

cpe:2.3:a:moodle:moodleSearch this product on Shodan

Exact CVE query

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Metadata

Canonical fields

NVD status

Unavailable

Published

Jan 21, 2026

Modified

Jun 17, 2026

Official record

Authoritative NVD record

CVSS vector

CVSS:4.0/AV:N/AC:L/AT:N/PR:L/UI:P/VC:L/VI:L/VA:N/SC:L/SI:L/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X

CWE IDs

Vendor classifications

How this vector reads

CVSS 4.0 base metrics decoded below. This explanation does not recalculate or change the NVD score.

Attack Vector (AV): Network. The vulnerable system can be reached across network boundaries.
Attack Complexity (AC): Low. No special conditions beyond the attacker-controlled steps are required.
Attack Requirements (AT): None. No prerequisite deployment or execution condition is required.
Privileges Required (PR): Low. The attacker needs basic user-level privileges.
User Interaction (UI): Passive. A targeted user must unknowingly interact with the vulnerable system.
Vulnerable System Confidentiality (VC): Low. There is a limited impact to this security property.
Vulnerable System Integrity (VI): Low. There is a limited impact to this security property.
Vulnerable System Availability (VA): None. There is no direct impact to this security property.
Subsequent System Confidentiality (SC): Low. There is a limited impact to this security property.
Subsequent System Integrity (SI): Low. There is a limited impact to this security property.
Subsequent System Availability (SA): None. There is no direct impact to this security property.

Optional CVSS v4 metrics remain in the raw vector; only base metrics are expanded here.

Signals

Exploitation indicators

0 stored signals · no KEV · 0 OTX pulses