CVE-2026-77399icalendar: Denial of service via unbounded VALARM REPEAT expansion
Updated under an hour ago ()
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No exploitation reported and no EPSS estimate yet.
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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
- 6.5 MEDIUM (v3.1, CNA)CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H
- Weakness (CWE)
- CWE-400, CWE-834
- Known exploited
- Not in CISA's KEV catalog
- EPSS (exploitation in the next 30 days)
- Not loaded for this CVE
- Assigned by
- GitHub_M
- NVD analysis
- Awaiting Analysis
- Record last updated
- Sep 23, 2026
- First seen by InfoSec Signals
- Oct 9, 2026
Affected products
collective icalendar collective:icalendar (from the name) | from 6.1.0, < 7.2.2 | CNA record |
References
- https://github.com/collective/icalendar/security/advisories/GHSA-qjcq-q7h7-r74vx-refsource-confirm
- https://github.com/collective/icalendar/pull/1571x-refsource-misc
- https://github.com/collective/icalendar/commit/157f85137c65565a308bbcf4fdcc7d8ebce01267x-refsource-misc
- https://github.com/collective/icalendar/commit/cddd37226adbc52cca52a399f61d38a378221219x-refsource-misc
- https://github.com/collective/icalendar/releases/tag/v7.2.2x-refsource-misc
The CVE record on cve.org NVD's entry
The CVE record is authoritative. Products marked “from the name” were identified from the CNA's free-text names, not a CPE, and are matched less certainly. This product uses the NVD API but is not endorsed or certified by the NVD.