{"cve":"CVE-2026-33635","nvd":{"published":"2026-03-26T21:17:07.287","modified":"2026-06-17T10:37:49.343","status":"Analyzed","description":"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.","cvss_v4":null,"cvss_v3":{"version":"3.1","vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:L/A:N","score":4.3},"cwes":["CWE-93"],"references":["https://github.com/icalendar/icalendar/commit/b8d23b490363ee5fffaec1d269a8618a912ca265","https://github.com/icalendar/icalendar/security/advisories/GHSA-pv9c-9mfh-hvxq","https://github.com/rubysec/ruby-advisory-db/blob/master/gems/icalendar/CVE-2026-33635.yml"],"products":["icalendar_project:icalendar"],"source":"nvd","synced_at":"2026-10-19T22:28:18.033120106+00:00"},"epss":{"cve":"CVE-2026-33635","score":0.00254,"percentile":0.16964,"date":"2026-11-01"},"kev":null,"osv":[{"id":"GHSA-pv9c-9mfh-hvxq","url":"https://osv.dev/vulnerability/GHSA-pv9c-9mfh-hvxq","summary":"iCalendar has ICS injection via unsanitized URI property values","modified":"2026-03-27T22:17:39.528683Z","packages":[{"ecosystem":"RubyGems","name":"icalendar","purl":"pkg:gem/icalendar","ranges":[">=2.0.0 <2.12.2"],"fixed":["2.12.2"]}]}],"attribution":["This product uses the NVD API but is not endorsed or certified by the NVD.","EPSS scores: FIRST Exploit Prediction Scoring System, https://www.first.org/epss","Known exploited vulnerabilities: CISA Known Exploited Vulnerabilities Catalog, https://www.cisa.gov/known-exploited-vulnerabilities-catalog","Package advisories: OSV (https://osv.dev), from the GitHub Advisory Database, PyPA, Go, RustSec and other ecosystem databases, under CC-BY 4.0 or CC0","CVE records: the CVE Program's CVE List (https://www.cve.org), under its terms of use (https://www.cve.org/Legal/TermsOfUse). CVE is a registered trademark of The MITRE Corporation; this product is not affiliated with the CVE Program."]}