{"id":"CVE-2026-33635","summary":"iCalendar has ICS injection via unsanitized URI property values","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.","aliases":["GHSA-pv9c-9mfh-hvxq"],"modified":"2026-04-02T13:27:56.015945Z","published":"2026-03-26T20:30:43.696Z","database_specific":{"cwe_ids":["CWE-93"],"cna_assigner":"GitHub_M","osv_generated_from":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/33xxx/CVE-2026-33635.json"},"references":[{"type":"ADVISORY","url":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/33xxx/CVE-2026-33635.json"},{"type":"FIX","url":"https://github.com/icalendar/icalendar/commit/b8d23b490363ee5fffaec1d269a8618a912ca265"},{"type":"ADVISORY","url":"https://github.com/icalendar/icalendar/security/advisories/GHSA-pv9c-9mfh-hvxq"},{"type":"ADVISORY","url":"https://github.com/rubysec/ruby-advisory-db/blob/master/gems/icalendar/CVE-2026-33635.yml"},{"type":"ADVISORY","url":"https://nvd.nist.gov/vuln/detail/CVE-2026-33635"}],"affected":[{"ranges":[{"type":"GIT","repo":"https://github.com/icalendar/icalendar","events":[{"introduced":"f7059c1695306dc7d39dd78e2903077a3112cb16"},{"fixed":"7782ac1bc174c240aa69d7a566112ed13af5a44a"}],"database_specific":{"versions":[{"introduced":"2.0.0"},{"fixed":"2.12.2"}]}}],"versions":["v2.0.0","v2.0.1","v2.1.0","v2.1.1","v2.1.2","v2.10.0","v2.10.1","v2.10.2","v2.10.3","v2.11.0","v2.11.1","v2.11.2","v2.12.0","v2.12.1","v2.2.0","v2.2.1","v2.2.2","v2.3.0","v2.4.0","v2.4.1","v2.5.0","v2.5.1","v2.5.2","v2.5.3","v2.6.0","v2.6.1","v2.7.0","v2.7.1","v2.8.0","v2.9.0"],"database_specific":{"source":"https://storage.googleapis.com/cve-osv-conversion/osv-output/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"}]}