CVE-2023-1647
📋 TL;DR
This CVE describes an improper access control vulnerability in Cal.com (formerly Calendly) scheduling software. It allows unauthorized users to bypass authentication mechanisms and access restricted functionality or data. All users running Cal.com versions prior to 2.7 are affected.
💻 Affected Systems
- Cal.com (formerly Calendly)
📦 What is this software?
⚠️ Risk & Real-World Impact
Worst Case
Attackers could gain unauthorized access to sensitive scheduling data, modify appointments, impersonate users, or potentially access administrative functions depending on the specific access control flaw.
Likely Case
Unauthorized viewing or modification of scheduling data, calendar manipulation, or access to user information that should be restricted.
If Mitigated
Proper authentication and authorization checks prevent unauthorized access, limiting users to their intended permissions and data scope.
🎯 Exploit Status
The vulnerability involves improper access control which typically requires some level of user interaction but minimal technical expertise to exploit once identified.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: 2.7 and later
Vendor Advisory: https://github.com/calcom/cal.com/security/advisories
Restart Required: Yes
Instructions:
1. Update Cal.com to version 2.7 or later
2. Restart the Cal.com application/service
3. Verify the update was successful by checking the version
🔧 Temporary Workarounds
Temporary Access Restriction
allImplement network-level restrictions to limit access to Cal.com instance
🧯 If You Can't Patch
- Implement strict network segmentation and firewall rules to limit access to Cal.com instances
- Enable detailed logging and monitoring for unauthorized access attempts to sensitive endpoints
🔍 How to Verify
Check if Vulnerable:
Check Cal.com version - if running version below 2.7, the system is vulnerableCheck Version:
Check package.json or application settings for version informationVerify Fix Applied:
Verify Cal.com version is 2.7 or higher and test authentication/authorization flows📡 Detection & Monitoring
Log Indicators:
- Unauthorized access attempts to restricted endpoints
- Authentication bypass patterns
- Unexpected user privilege escalations
Network Indicators:
- Unusual API calls to sensitive endpoints
- Requests bypassing expected authentication flows
SIEM Query:
source="cal.com" AND (event="unauthorized_access" OR status="403" OR user_privilege_change="true")🔗 References
- https://github.com/sbs20/scanservjs/pull/606/commits/d51fd52c1569813990b8f74e64ae6979c665dca1
- https://huntr.dev/bounties/d6de3d6e-9551-47d1-b28c-7e965c1b82b6
- https://github.com/sbs20/scanservjs/pull/606/commits/d51fd52c1569813990b8f74e64ae6979c665dca1
- https://huntr.dev/bounties/d6de3d6e-9551-47d1-b28c-7e965c1b82b6
