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CVE-2026-77399

6.5 · MEDIUM

icalendar is an RFC 5545 compatible parser and generator of iCalendar files for Python.

Published Sep 22, 2026CWE-400EPSS 0.31%

Overview

CVE-2026-77399 is a medium-severity vulnerability. It was published on September 22, 2026 and has a CVSS 3.1 base score of 6.5 (MEDIUM).

This vulnerability has a CVSS 3.1 base score of 6.5, rated MEDIUM. It can be exploited remotely over the network. Some level of privileges is required for exploitation.

Technical 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.

Remediation

Check the references section for vendor advisories, patches, and mitigation guidance. If immediate patching is not possible, review the CVSS vector to understand the attack surface and apply compensating controls such as network segmentation or access restrictions.

References

GitHubgithub.com/collective/icalendar/commit/157f85137c65565a308bbcf4fdcc7d8ebce01267GitHubgithub.com/collective/icalendar/commit/cddd37226adbc52cca52a399f61d38a378221219GitHubgithub.com/collective/icalendar/pull/1571GitHubgithub.com/collective/icalendar/releases/tag/v7.2.2GitHubgithub.com/collective/icalendar/security/advisories/GHSA-qjcq-q7h7-r74v

How CyberStrike helps

Frequently asked questions

What is CVE-2026-77399?

CVE-2026-77399 is a medium-severity vulnerability. It was published on September 22, 2026 and has a CVSS 3.1 base score of 6.5 (MEDIUM).

How severe is CVE-2026-77399?

This vulnerability has a CVSS 3.1 base score of 6.5, rated MEDIUM. It can be exploited remotely over the network. Some level of privileges is required for exploitation.

How do I fix or remediate CVE-2026-77399?

Check the references section for vendor advisories, patches, and mitigation guidance. If immediate patching is not possible, review the CVSS vector to understand the attack surface and apply compensating controls such as network segmentation or access restrictions.

How can CyberStrike help with CVE-2026-77399?

CyberStrike is an open-source, AI-augmented pentesting engine. Rather than flag a version number, it tests whether an issue like CVE-2026-77399 is actually reachable in your own applications and APIs, then verifies each finding before reporting it. That tells you if the weakness is a real, exploitable risk in your environment or a false positive you can safely deprioritize.

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