Nextcloud Calendar up to 6.0.2 Meeting Proposal random values

CVSS Meta Temp Score
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Current Exploit Price (≈)
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CTI Interest Score
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5.0$0-$5k0.00

Summaryinfo

A vulnerability was found in Nextcloud Calendar up to 6.0.2. It has been rated as problematic. Affected is an unknown function of the component Meeting Proposal Handler. Performing a manipulation results in random values. This vulnerability is cataloged as CVE-2025-66511. It is possible to initiate the attack remotely. There is no exploit available. Upgrading the affected component is advised.

Detailsinfo

A vulnerability was found in Nextcloud Calendar up to 6.0.2. It has been classified as problematic. This affects an unknown function of the component Meeting Proposal Handler. The manipulation with an unknown input leads to a random values vulnerability. CWE is classifying the issue as CWE-330. The product uses insufficiently random numbers or values in a security context that depends on unpredictable numbers. This is going to have an impact on confidentiality. The summary by CVE is:

Nextcloud Calendar is a calendar app for Nextcloud. Prior to 6.0.3, the Calendar app generates participant tokens for meeting proposals using a hash function, allowing an attacker to compute valid participant tokens, which allowed them to request details and submit dates in meeting proposals. The tokens are not purely random generated. This vulnerability is fixed in 6.0.3.

The advisory is shared at github.com. This vulnerability is uniquely identified as CVE-2025-66511 since 12/03/2025. The exploitability is told to be difficult. It is possible to initiate the attack remotely. No form of authentication is needed for exploitation. Neither technical details nor an exploit are publicly available. MITRE ATT&CK project uses the attack technique T1600.001 for this issue.

Upgrading to version 6.0.3 eliminates this vulnerability.

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Productinfo

Type

Vendor

Name

Version

License

CPE 2.3info

CPE 2.2info

CVSSv4info

VulDB Vector: 🔒
VulDB Reliability: 🔍

CVSSv3info

VulDB Meta Base Score: 5.0
VulDB Meta Temp Score: 5.0

VulDB Base Score: 3.7
VulDB Temp Score: 3.6
VulDB Vector: 🔒
VulDB Reliability: 🔍

NVD Base Score: 6.5
NVD Vector: 🔒

CNA Base Score: 4.8
CNA Vector (GitHub_M): 🔒

CVSSv2info

AVACAuCIA
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VectorComplexityAuthenticationConfidentialityIntegrityAvailability
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VulDB Base Score: 🔒
VulDB Temp Score: 🔒
VulDB Reliability: 🔍

Exploitinginfo

Class: Random values
CWE: CWE-330 / CWE-310
CAPEC: 🔒
ATT&CK: 🔒

Physical: No
Local: No
Remote: Yes

Availability: 🔒
Status: Not defined

EPSS Score: 🔒
EPSS Percentile: 🔒

Price Prediction: 🔍
Current Price Estimation: 🔒

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Threat Intelligenceinfo

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

Countermeasuresinfo

Recommended: Upgrade
Status: 🔍

0-Day Time: 🔒

Upgrade: Calendar 6.0.3

Timelineinfo

12/03/2025 CVE reserved
12/05/2025 +2 days Advisory disclosed
12/05/2025 +0 days VulDB entry created
12/11/2025 +6 days VulDB entry last update

Sourcesinfo

Advisory: github.com
Status: Confirmed

CVE: CVE-2025-66511 (🔒)
GCVE (CVE): GCVE-0-2025-66511
GCVE (VulDB): GCVE-100-334509

Entryinfo

Created: 12/05/2025 17:58
Updated: 12/11/2025 03:51
Changes: 12/05/2025 17:58 (65), 12/11/2025 03:51 (11)
Complete: 🔍
Cache ID: 216::103

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