{
  "affected": [
    {
      "ranges": [
        {
          "database_specific": {
            "versions": [
              {
                "introduced": "2.0.0"
              },
              {
                "fixed": "2.12.2"
              }
            ]
          },
          "events": [
            {
              "introduced": "f7059c1695306dc7d39dd78e2903077a3112cb16"
            },
            {
              "fixed": "7782ac1bc174c240aa69d7a566112ed13af5a44a"
            }
          ],
          "repo": "https://github.com/icalendar/icalendar",
          "type": "GIT"
        }
      ]
    }
  ],
  "aliases": [
    "GHSA-pv9c-9mfh-hvxq"
  ],
  "database_specific": {
    "cna_assigner": "GitHub_M",
    "cwe_ids": [
      "CWE-93"
    ],
    "osv_generated_from": "https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/33xxx/CVE-2026-33635.json"
  },
  "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.",
  "id": "CVE-2026-33635",
  "modified": "2026-04-01T23:09:35.638315741Z",
  "published": "2026-03-26T20:30:43.696Z",
  "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"
    }
  ],
  "schema_version": "1.7.3",
  "severity": [
    {
      "score": "CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:L/A:N",
      "type": "CVSS_V3"
    }
  ],
  "summary": "iCalendar has ICS injection via unsanitized URI property values"
}