{"dataType": "CVE_RECORD", "dataVersion": "5.2", "cveMetadata": {"cveId": "CVE-2026-33635", "assignerOrgId": "a0819718-46f1-4df5-94e2-005712e83aaa", "state": "PUBLISHED", "assignerShortName": "GitHub_M", "dateReserved": "2026-03-23T14:24:11.619Z", "datePublished": "2026-03-26T20:30:43.696Z", "dateUpdated": "2026-03-26T20:30:43.696Z"}, "containers": {"cna": {"title": "iCalendar has ICS injection via unsanitized URI property values", "problemTypes": [{"descriptions": [{"cweId": "CWE-93", "lang": "en", "description": "CWE-93: Improper Neutralization of CRLF Sequences ('CRLF Injection')", "type": "CWE"}]}], "metrics": [{"cvssV3_1": {"attackComplexity": "LOW", "attackVector": "NETWORK", "availabilityImpact": "NONE", "baseScore": 4.3, "baseSeverity": "MEDIUM", "confidentialityImpact": "NONE", "integrityImpact": "LOW", "privilegesRequired": "NONE", "scope": "UNCHANGED", "userInteraction": "REQUIRED", "vectorString": "CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:L/A:N", "version": "3.1"}}], "references": [{"name": "https://github.com/icalendar/icalendar/security/advisories/GHSA-pv9c-9mfh-hvxq", "tags": ["x_refsource_CONFIRM"], "url": "https://github.com/icalendar/icalendar/security/advisories/GHSA-pv9c-9mfh-hvxq"}, {"name": "https://github.com/icalendar/icalendar/commit/b8d23b490363ee5fffaec1d269a8618a912ca265", "tags": ["x_refsource_MISC"], "url": "https://github.com/icalendar/icalendar/commit/b8d23b490363ee5fffaec1d269a8618a912ca265"}, {"name": "https://github.com/rubysec/ruby-advisory-db/blob/master/gems/icalendar/CVE-2026-33635.yml", "tags": ["x_refsource_MISC"], "url": "https://github.com/rubysec/ruby-advisory-db/blob/master/gems/icalendar/CVE-2026-33635.yml"}], "affected": [{"vendor": "icalendar", "product": "icalendar", "versions": [{"version": ">= 2.0.0, < 2.12.2", "status": "affected"}]}], "providerMetadata": {"orgId": "a0819718-46f1-4df5-94e2-005712e83aaa", "shortName": "GitHub_M", "dateUpdated": "2026-03-26T20:30:43.696Z"}, "descriptions": [{"lang": "en", "value": "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."}], "source": {"advisory": "GHSA-pv9c-9mfh-hvxq", "discovery": "UNKNOWN"}}}}

{}

{"cveTags": [], "descriptions": [{"lang": "en", "value": "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", "lastModified": "2026-03-26T21:17:07.287", "metrics": {"cvssMetricV31": [{"cvssData": {"attackComplexity": "LOW", "attackVector": "NETWORK", "availabilityImpact": "NONE", "baseScore": 4.3, "baseSeverity": "MEDIUM", "confidentialityImpact": "NONE", "integrityImpact": "LOW", "privilegesRequired": "NONE", "scope": "UNCHANGED", "userInteraction": "REQUIRED", "vectorString": "CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:L/A:N", "version": "3.1"}, "exploitabilityScore": 2.8, "impactScore": 1.4, "source": "security-advisories@github.com", "type": "Secondary"}]}, "published": "2026-03-26T21:17:07.287", "references": [{"source": "security-advisories@github.com", "url": "https://github.com/icalendar/icalendar/commit/b8d23b490363ee5fffaec1d269a8618a912ca265"}, {"source": "security-advisories@github.com", "url": "https://github.com/icalendar/icalendar/security/advisories/GHSA-pv9c-9mfh-hvxq"}, {"source": "security-advisories@github.com", "url": "https://github.com/rubysec/ruby-advisory-db/blob/master/gems/icalendar/CVE-2026-33635.yml"}], "sourceIdentifier": "security-advisories@github.com", "vulnStatus": "Received", "weaknesses": [{"description": [{"lang": "en", "value": "CWE-93"}], "source": "security-advisories@github.com", "type": "Primary"}]}

{}

{}