Vulnerability 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.
CVSS Score
MEDIUM
Related Weaknesses (CWE)
References
- https://github.com/collective/icalendar/commit/157f85137c65565a308bbcf4fdcc7d8eb
- https://github.com/collective/icalendar/commit/cddd37226adbc52cca52a399f61d38a37
- https://github.com/collective/icalendar/pull/1571
- https://github.com/collective/icalendar/releases/tag/v7.2.2
- https://github.com/collective/icalendar/security/advisories/GHSA-qjcq-q7h7-r74v
FAQ
What is CVE-2026-77399?
CVE-2026-77399 is a vulnerability with a CVSS score of 6.5 (MEDIUM). 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 ...
How severe is CVE-2026-77399?
CVE-2026-77399 has been rated MEDIUM with a CVSS base score of 6.5/10. Review the CVSS metrics above for detailed severity breakdown.
Is there a patch for CVE-2026-77399?
Check the references section above for vendor advisories and patch information. Review vendor security bulletins for remediation guidance.