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Resource Exhaustion Affecting python-icalendar package, versions <7.3.0-1

Severity

 Recommended
low

Based on default assessment until relevant scores are available.

Threat Intelligence

EPSS
0.31% (22nd percentile)

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  • Snyk IDSNYK-DEBIANUNSTABLE-PYTHONICALENDAR-20067656
  • published24 Sept 2026
  • disclosed22 Sept 2026
Report a new vulnerability Found a mistake?

Introduced: 22 Sep 2026

CVE-2026-77399  (opens in a new tab)
CWE-400  (opens in a new tab)
CWE-834  (opens in a new tab)

How to fix?

Upgrade Debian:unstable python-icalendar to version 7.3.0-1 or higher.

NVD Description

Note: Versions mentioned in the description apply only to the upstream python-icalendar package and not the python-icalendar package as distributed by Debian. See How to fix? for Debian:unstable relevant fixed versions and status.

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.