CVE-2026-77399

Name	CVE-2026-77399
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.
Source	CVE (at NVD; CERT, ENISA, LWN, oss-sec, fulldisc, Debian ELTS, Red Hat, Ubuntu, Gentoo, SUSE bugzilla/CVE, GitHub advisories/code/issues, web search, more)
Debian Bugs	1148817

Vulnerable and fixed packages

The table below lists information on source packages.

Source Package	Release	Version	Status
python-icalendar (PTS)	bookworm	4.0.3-5	fixed
	trixie	6.0.1-2	fixed
	forky, sid	6.3.1-2	vulnerable

The information below is based on the following data on fixed versions.

Package	Type	Release	Fixed Version	Debian Bugs
python-icalendar	source	bookworm	(not affected)
python-icalendar	source	trixie	(not affected)
python-icalendar	source	(unstable)	(unfixed)	1148817

Notes

[trixie] - python-icalendar <not-affected> (Vulnerable code not present, introduced in 6.1.0)
[bookworm] - python-icalendar <not-affected> (Vulnerable code not present, introduced in 6.1.0)
https://github.com/collective/icalendar/security/advisories/GHSA-qjcq-q7h7-r74v
https://github.com/collective/icalendar/pull/1571
https://github.com/collective/icalendar/commit/157f85137c65565a308bbcf4fdcc7d8ebce01267 (v7.2.1)