Medium
python-icalendar — security advisory
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.
- Products
- python-icalendar
- Affected versions
- 3.11.7-3, 3.8-1, 3.8-2, 4.0.0-1, 4.0.3-3, 4.0.3-4, 5.0.11-1, 5.0.7-1, 6.0.1-3, 6.3.1-1, 6.3.1-2
- Fixed versions
- Not specified
- CVEs
- CVE-2026-77399
- Confirmed fixed CVEs
- Not specified
- Updated in this feed
- 31 Oct 2026, 03:19 UTC · Revision 1
Source evidence
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.
osv:UBUNTU-CVE-2026-77399
python-icalendar
Fixed versions: Not specified
python-icalendar
Fixed versions: Not specified
python-icalendar
Fixed versions: Not specified
python-icalendar
Fixed versions: Not specified
python-icalendar
Fixed versions: Not specified
python-icalendar
Fixed versions: Not specified
python-icalendar
Fixed versions: Not specified
Complete source record
{
"id": "f3013e5f292f0e3fa4f077ed1b9121bf0fd049087c6ce82dca1500e854c64888",
"url": "https://osv.dev/vulnerability/UBUNTU-CVE-2026-77399",
"method": "structured",
"payload": {
"kind": "advisory",
"title": "UBUNTU-CVE-2026-77399",
"summary": "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.",
"evidence": "osv:UBUNTU-CVE-2026-77399",
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"severity": "medium",
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"aliases": [
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"metrics": [
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"score": "CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H"
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{
"type": "Ubuntu",
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},
"versions": [
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"database_specific": {
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"ecosystem": "Ubuntu:20.04:LTS"
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"modified": "2026-10-17T13:01:07.839488067Z",
"provider": "osv",
"upstream": [
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],
"references": [
"https://ubuntu.com/security/CVE-2026-77399",
"https://www.cve.org/CVERecord?id=CVE-2026-77399",
"https://github.com/collective/icalendar/commit/157f85137c65565a308bbcf4fdcc7d8ebce01267",
"https://github.com/collective/icalendar/commit/cddd37226adbc52cca52a399f61d38a378221219",
"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"
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"evidence": "/upstream"
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"security_relevant": true,
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"source_id": "core-osv",
"document_id": 361037,
"published_at": "2026-09-22T19:16:00+00:00"
}