CVE catalog

CVE-2026-77399

icalendar is an RFC 5545 compatible parser and…

[CVE catalog]

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.

Severity
Medium · CVSS 6.5CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H
Published
Updated
Source
[NVD] · [CVE record]
EPSS
0.31% · Oct 27, 2026

Projects and upstream resources

Reported versions and fixes

Each observation applies to its named package, distribution, and release. Distribution backports can fix a vulnerability while retaining an older upstream version number.

Version impact has not been established. The original provider fields are retained below.

Provider details and historical evidence
Original provider fields
{
  "package_releases": [
    {
      "name": "python-icalendar",
      "status": "fixed",
      "release": "sid",
      "version": "7.3.0-1"
    },
    {
      "name": "python-icalendar",
      "status": "fixed",
      "release": "forky",
      "version": "7.3.0-1"
    },
    {
      "name": "python-icalendar",
      "status": "not affected",
      "release": "trixie",
      "version": "6.0.1-2"
    },
    {
      "name": "python-icalendar",
      "status": "not affected",
      "release": "bookworm",
      "version": "4.0.3-5"
    }
  ],
  "fixed_versions": [
    {
      "bug": 1148817,
      "name": "python-icalendar",
      "type": "source",
      "origin": null,
      "release": "sid",
      "urgency": "not yet assigned",
      "fixed_version": "7.3.0-1"
    },
    {
      "bug": 1148817,
      "name": "python-icalendar",
      "type": "source",
      "origin": null,
      "release": "forky",
      "urgency": "not yet assigned",
      "fixed_version": "7.3.0-1"
    },
    {
      "bug": 1148817,
      "name": "python-icalendar",
      "type": "source",
      "origin": null,
      "release": "trixie",
      "urgency": "unimportant",
      "fixed_version": "0"
    },
    {
      "bug": 1148817,
      "name": "python-icalendar",
      "type": "source",
      "origin": null,
      "release": "bookworm",
      "urgency": "unimportant",
      "fixed_version": "0"
    }
  ],
  "distribution_packages": []
}

[Debian bug #1148817]

OpenFactory catalog packages

Matching against OpenFactory catalog package versions is in progress.

[Debian 12 (Bookworm)]

  • [python3-icalendar]Unknown

    Source package: [python-icalendar]

    Details (2)

    • 4.0.3-5 · all · bookworm

      Not affected

      nvd · python-icalendar · debian · bookworm

    • 4.0.3-5 · all · bookworm

      Not affected

      nvd · python-icalendar · debian · bookworm

  • [python-icalendar-doc]Unknown

    Source package: [python-icalendar]

    Details (2)

    • 4.0.3-5 · all · bookworm

      Not affected

      nvd · python-icalendar · debian · bookworm

    • 4.0.3-5 · all · bookworm

      Not affected

      nvd · python-icalendar · debian · bookworm

Observed:

References

[Debian Security Tracker] · [FIRST EPSS] · [National Vulnerability Database (NVD)] · [OSV Package Vulnerability Database]