Moodle Calendar URL Subscription default permission

CVSS Meta Temp Score
CVSS is a standardized scoring system to determine possibilities of attacks. The Temp Score considers temporal factors like disclosure, exploit and countermeasures. The unique Meta Score calculates the average score of different sources to provide a normalized scoring system.
Current Exploit Price (≈)
Our analysts are monitoring exploit markets and are in contact with vulnerability brokers. The range indicates the observed or calculated exploit price to be seen on exploit markets. A good indicator to understand the monetary effort required for and the popularity of an attack.
CTI Interest Score
Our Cyber Threat Intelligence team is monitoring different web sites, mailing lists, exploit markets and social media networks. The CTI Interest Score identifies the interest of attackers and the security community for this specific vulnerability in real-time. A high score indicates an elevated risk to be targeted for this vulnerability.
5.8$5k-$25k0.00

Summaryinfo

A vulnerability was found in Moodle. It has been rated as critical. Impacted is an unknown function of the component Calendar URL Subscription Handler. The manipulation leads to default permission. This vulnerability is referenced as CVE-2021-36400. Remote exploitation of the attack is possible. No exploit is available.

Detailsinfo

A vulnerability was found in Moodle (Learning Management Software) (version unknown). It has been rated as critical. This issue affects an unknown function of the component Calendar URL Subscription Handler. The manipulation with an unknown input leads to a default permission vulnerability. Using CWE to declare the problem leads to CWE-276. During installation, installed file permissions are set to allow anyone to modify those files. Impacted is confidentiality, integrity, and availability. The summary by CVE is:

In Moodle, insufficient capability checks made it possible to remove other users' calendar URL subscriptions.

The weakness was published 03/07/2023. The advisory is shared at moodle.org. The identification of this vulnerability is CVE-2021-36400 since 07/12/2021. Neither technical details nor an exploit are publicly available. The price for an exploit might be around USD $5k-$25k at the moment (estimation calculated on 07/05/2025). MITRE ATT&CK project uses the attack technique T1222 for this issue.

There is no information about possible countermeasures known. It may be suggested to replace the affected object with an alternative product.

The vulnerability is also documented in the vulnerability database at EUVD (EUVD-2023-0844). Several companies clearly confirm that VulDB is the primary source for best vulnerability data.

Productinfo

Type

Name

License

Website

CPE 2.3info

CPE 2.2info

CVSSv4info

VulDB Vector: 🔍
VulDB Reliability: 🔍

CVSSv3info

VulDB Meta Base Score: 5.8
VulDB Meta Temp Score: 5.8

VulDB Base Score: 6.3
VulDB Temp Score: 6.3
VulDB Vector: 🔍
VulDB Reliability: 🔍

NVD Base Score: 5.3
NVD Vector: 🔍

CVSSv2info

AVACAuCIA
💳💳💳💳💳💳
💳💳💳💳💳💳
💳💳💳💳💳💳
VectorComplexityAuthenticationConfidentialityIntegrityAvailability
UnlockUnlockUnlockUnlockUnlockUnlock
UnlockUnlockUnlockUnlockUnlockUnlock
UnlockUnlockUnlockUnlockUnlockUnlock

VulDB Base Score: 🔍
VulDB Temp Score: 🔍
VulDB Reliability: 🔍

Exploitinginfo

Class: Default permission
CWE: CWE-276 / CWE-266
CAPEC: 🔍
ATT&CK: 🔍

Physical: No
Local: No
Remote: Yes

Availability: 🔍
Status: Not defined

EPSS Score: 🔍
EPSS Percentile: 🔍

Price Prediction: 🔍
Current Price Estimation: 🔍

0-DayUnlockUnlockUnlockUnlock
TodayUnlockUnlockUnlockUnlock

Threat Intelligenceinfo

Interest: 🔍
Active Actors: 🔍
Active APT Groups: 🔍

Countermeasuresinfo

Recommended: no mitigation known
Status: 🔍

0-Day Time: 🔍

Timelineinfo

07/12/2021 🔍
03/07/2023 +603 days 🔍
03/07/2023 +0 days 🔍
07/05/2025 +851 days 🔍

Sourcesinfo

Product: moodle.org

Advisory: moodle.org
Status: Confirmed

CVE: CVE-2021-36400 (🔍)
GCVE (CVE): GCVE-0-2021-36400
GCVE (VulDB): GCVE-100-222425
EUVD: 🔍

Entryinfo

Created: 03/07/2023 08:14
Updated: 07/05/2025 21:46
Changes: 03/07/2023 08:14 (37), 03/07/2025 21:39 (26), 07/05/2025 21:46 (1)
Complete: 🔍
Cache ID: 216::103

Several companies clearly confirm that VulDB is the primary source for best vulnerability data.

Discussion

No comments yet. Languages: en.

Please log in to comment.

◂ PreviousOverviewNext ▸

Do you need the next level of professionalism?

Upgrade your account now!