{"id":"UBUNTU-CVE-2026-33635","details":"iCalendar is a Ruby library for dealing with iCalendar files in the iCalendar format defined by RFC-5545. Starting in version 2.0.0 and prior to version 2.12.2, .ics serialization does not properly sanitize URI property values, enabling ICS injection through attacker-controlled input, adding arbitrary calendar lines to the output. `Icalendar::Values::Uri` falls back to the raw input string when `URI.parse` fails and later serializes it with `value.to_s` without removing or escaping `\\r` or `\\n` characters. That value is embedded directly into the final ICS line by the normal serializer, so a payload containing CRLF can terminate the original property and create a new ICS property or component. (It looks like you can inject via url, source, image, organizer, attach, attendee, conference, tzurl because of this). Applications that generate `.ics` files from partially untrusted metadata are impacted. As a result, downstream calendar clients or importers may process attacker-supplied content as if it were legitimate event data, such as added attendees, modified URLs, alarms, or other calendar fields. Version 2.12.2 contains a patch for the issue.","modified":"2026-04-14T11:03:23.879612Z","published":"2026-03-26T21:17:00Z","upstream":["CVE-2026-33635"],"references":[{"type":"REPORT","url":"https://ubuntu.com/security/CVE-2026-33635"},{"type":"REPORT","url":"https://www.cve.org/CVERecord?id=CVE-2026-33635"},{"type":"REPORT","url":"https://github.com/icalendar/icalendar/security/advisories/GHSA-pv9c-9mfh-hvxq"},{"type":"REPORT","url":"https://github.com/icalendar/icalendar/commit/b8d23b490363ee5fffaec1d269a8618a912ca265"},{"type":"REPORT","url":"https://github.com/rubysec/ruby-advisory-db/blob/master/gems/icalendar/CVE-2026-33635.yml"}],"affected":[{"package":{"name":"ruby-icalendar","ecosystem":"Ubuntu:20.04:LTS","purl":"pkg:deb/ubuntu/ruby-icalendar@2.4.1-2?arch=source&distro=focal"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"}]}],"versions":["2.4.1-2"],"ecosystem_specific":{"binaries":[{"binary_name":"ruby-icalendar","binary_version":"2.4.1-2"}]},"database_specific":{"source":"https://github.com/canonical/ubuntu-security-notices/blob/main/osv/cve/2026/UBUNTU-CVE-2026-33635.json"}},{"package":{"name":"ruby-icalendar","ecosystem":"Ubuntu:22.04:LTS","purl":"pkg:deb/ubuntu/ruby-icalendar@2.7.1-1?arch=source&distro=jammy"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"}]}],"versions":["2.4.1-2","2.7.1-1"],"ecosystem_specific":{"binaries":[{"binary_name":"ruby-icalendar","binary_version":"2.7.1-1"}]},"database_specific":{"source":"https://github.com/canonical/ubuntu-security-notices/blob/main/osv/cve/2026/UBUNTU-CVE-2026-33635.json"}},{"package":{"name":"ruby-icalendar","ecosystem":"Ubuntu:24.04:LTS","purl":"pkg:deb/ubuntu/ruby-icalendar@2.10.0-1?arch=source&distro=noble"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"}]}],"versions":["2.8.0-1","2.10.0-1"],"ecosystem_specific":{"binaries":[{"binary_name":"ruby-icalendar","binary_version":"2.10.0-1"}]},"database_specific":{"source":"https://github.com/canonical/ubuntu-security-notices/blob/main/osv/cve/2026/UBUNTU-CVE-2026-33635.json"}}],"schema_version":"1.7.5","severity":[{"type":"CVSS_V3","score":"CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:L/A:N"},{"type":"CVSS_V3","score":"CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:L/A:N"},{"type":"Ubuntu","score":"medium"}]}