CVE-2026-77399

medium

Assigned by CNA: github_m

Published 2026-09-22 · Modified 2026-09-22

Discuss on Community Propose mitigation

CVSS v3

6.5

CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H

CVSS v4 NEW

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not yet in upstream

VIR risk

6.5

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.

Predictions

Exploit likelihood

75%

Patch ETA

—

Heuristic predictions, AS-IS, for prioritization only.

Mitigations

No mitigations published for this CVE yet.

The vendor-content worker queues fetches as references arrive (check back in a few minutes). Or — if you've already worked around this in production — publish your fix to the community-verified tier.

Propose a mitigation on Community Mitigations published via the community go through AI scoring + 2 human reviewers + 7-day silent objection window before landing here with source_tier=community-verified.

References

CWEs

CWE-400 CWE-834

Community-verified mitigations for this CVE will appear above when contributors publish them.

Verify integrity in audit chain (admin only). AS-IS.