Publish GHSA-pv9c-9mfh-hvxq

Author: advisory-database[bot]

advisories/github-reviewed/2026/03/GHSA-pv9c-9mfh-hvxq/GHSA-pv9c-9mfh-hvxq.json

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+{
+  "schema_version": "1.4.0",
+  "id": "GHSA-pv9c-9mfh-hvxq",
+  "modified": "2026-03-24T19:13:41Z",
+  "published": "2026-03-24T19:13:41Z",
+  "aliases": [
+    "CVE-2026-33635"
+  ],
+  "summary": "iCalendar has ICS injection via unsanitized URI property values",
+  "details": "### Summary\n.ics serialization does not properly sanitize URI property values, enabling ICS injection through attacker-controlled input, adding arbitrary calendar lines to the output.\n\n### Details\n`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)\n\nRelevant code:\n- `lib/icalendar/values/uri.rb:16`\n\n### PoC\nRun the following with the library loaded:\n\n```ruby\nrequire \"icalendar/value\"\nrequire \"icalendar/values/uri\"\n\nv = Icalendar::Values::Uri.new(\"https://a.example/ok\\r\\nATTENDEE:mailto:evil@example.com\")\nputs v.to_ical(Icalendar::Values::Text)\n```\n\noutput:\n\n```text\n;VALUE=URI:https://a.example/ok\nATTENDEE:mailto:evil@example.com\n```\n\n### Impact\nApplications 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.\n\n## Fix\nReject raw CR and LF characters in `URI`-typed values before serialization, or escape/encode them so they cannot terminate the current ICS content line.",
+  "severity": [
+    {
+      "type": "CVSS_V3",
+      "score": "CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:L/A:N"
+    }
+  ],
+  "affected": [
+    {
+      "package": {
+        "ecosystem": "RubyGems",
+        "name": "icalendar"
+      },
+      "ranges": [
+        {
+          "type": "ECOSYSTEM",
+          "events": [
+            {
+              "introduced": "2.0.0"
+            },
+            {
+              "fixed": "2.12.2"
+            }
+          ]
+        }
+      ]
+    }
+  ],
+  "references": [
+    {
+      "type": "WEB",
+      "url": "https://github.com/icalendar/icalendar/security/advisories/GHSA-pv9c-9mfh-hvxq"
+    },
+    {
+      "type": "WEB",
+      "url": "https://github.com/icalendar/icalendar/commit/b8d23b490363ee5fffaec1d269a8618a912ca265"
+    },
+    {
+      "type": "PACKAGE",
+      "url": "https://github.com/icalendar/icalendar"
+    }
+  ],
+  "database_specific": {
+    "cwe_ids": [
+      "CWE-93"
+    ],
+    "severity": "MODERATE",
+    "github_reviewed": true,
+    "github_reviewed_at": "2026-03-24T19:13:41Z",
+    "nvd_published_at": null
+  }
+}