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.
History

Wed, 23 Sep 2026 15:30:00 +0000

Type Values Removed Values Added
Metrics ssvc

{'options': {'Automatable': 'no', 'Exploitation': 'none', 'Technical Impact': 'partial'}, 'version': '2.0.3'}


Tue, 22 Sep 2026 21:30:00 +0000

Type Values Removed Values Added
First Time appeared Collective
Collective icalendar
Vendors & Products Collective
Collective icalendar

Tue, 22 Sep 2026 19:15:00 +0000

Type Values Removed Values Added
Description 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.
Title icalendar: Denial of service via unbounded VALARM REPEAT expansion
Weaknesses CWE-400
CWE-834
References
Metrics cvssV3_1

{'score': 6.5, 'vector': 'CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H'}


cve-icon MITRE

Status: PUBLISHED

Assigner: GitHub_M

Published: 2026-09-22T18:58:56.647Z

Updated: 2026-09-23T14:36:47.671Z

Reserved: 2026-08-20T19:55:27.023Z

Link: CVE-2026-77399

cve-icon Vulnrichment

Updated: 2026-09-23T14:10:15.008Z

cve-icon NVD

Status : Awaiting Analysis

Published: 2026-09-22T19:16:51.443

Modified: 2026-09-23T18:12:04.247

Link: CVE-2026-77399

cve-icon Redhat

No data.