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CVE-2026-77399

icalendar: Denial of service via unbounded VALARM REPEAT expansion PUBLISHED

Description (CNA)

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.

Affected (CNA)

Vendor / productVersions
collective / icalendaraffected >= 6.1.0, < 7.2.2

CWE

CWE-400, CWE-834

References

ADP enrichment

CISA-ADP

No English description supplied.

No references supplied.