icalendar is an RFC 5545 compatible parser and generator of iCalendar files for Python. From 6.1.0 until 7.2.2, vInt.from_ical accepts an attacker-controlled VALARM REPEAT value and applications that request alarm times can eagerly expand it without an application-level limit. Alarms.times and Alarms.active reach the unbounded expansion in versions starting with 6.1.0, while Alarm.triggers adds a second affected path starting with 7.0.0.
Parsing alone does not trigger the issue, but accessing these properties can consume excessive CPU time and heap memory and terminate or stall a service. This issue is fixed in version 7.2.2.
Attack Parameters
Attack Vector
Network
Can be exploited remotely
Attack Complexity
Low
Easy to exploit
Privileges Required
Low
Basic privileges needed
User Interaction
None
No user interaction needed
Impact Assessment
Confidentiality
None
No data leak
Integrity
None
No data modification
Availability
High
Complete denial of service
CVSS Vector v3.1
Weakness Type (CWE)
References 5
https://github.com/collective/icalendar/commit/157f85137c65565a308bbcf4fdcc7d8e…
security-advisories@github.com
https://github.com/collective/icalendar/commit/cddd37226adbc52cca52a399f61d38a3…
security-advisories@github.com
https://github.com/collective/icalendar/pull/1571
security-advisories@github.com
https://github.com/collective/icalendar/releases/tag/v7.2.2
security-advisories@github.com
https://github.com/collective/icalendar/security/advisories/GHSA-qjcq-q7h7-r74v
security-advisories@github.com