CVE-2026-39369: WWBN/AVideo WWBN AVideo's GIF Poster Fetch Vulnerability

{
  "schema_version" : "1.4.0",
  "id" : "GHSA-f4f9-627c-jh33",
  "modified" : "2026-04-24T21:10:48Z",
  "published" : "2026-04-08T00:08:44Z",
  "aliases" : [ "CVE-2026-39369" ],
  "summary" : "WWBN AVideo's GIF poster fetch bypasses traversal scrubbing and exposes local files through public media URLs",
  "details" : "## Summary\n\n`objects/aVideoEncoderReceiveImage.json.php` allowed an authenticated uploader to fetch attacker-controlled same-origin `/videos/...` URLs, bypass traversal scrubbing, and expose server-local files through the GIF poster storage path.\n\nThe vulnerable GIF branch could be abused to read local files such as `/etc/passwd` or application source files and republish those bytes through a normal public GIF media URL.\n\n## Details\n\nThe vulnerable chain was:\n\n1. `objects/aVideoEncoderReceiveImage.json.php` accepted attacker-controlled `downloadURL_gifimage`\n2. traversal scrubbing used `str_replace('../', '', ...)`, which was bypassable with overlapping input such as `....//`\n3. same-origin `/videos/...` URLs were accepted\n4. `url_get_contents()` and `try_get_contents_from_local()` resolved the request into a local filesystem read\n5. the fetched bytes were written into the GIF destination\n6. invalid GIF cleanup used the wrong variable, so the non-image payload remained on disk\n\nThis made the GIF poster path a local file disclosure primitive with public retrieval.\n\n## Proof of concept\n\n1. Log in as an uploader and create an owned video row through the normal encoder flow.\n2. Send:\n\n```text\nPOST /objects/aVideoEncoderReceiveImage.json.php\ndownloadURL_gifimage=https://localhost/videos/....//....//....//....//....//....//etc/passwd\n```\n\n3. Query:\n\n```text\nGET /objects/videos.json.php?showAll=1\n```\n\n4. Recover the generated GIF URL from `videosURL.gif.url`.\n5. Download that GIF URL.\n6. Observe that the body matches the target local file, such as `/etc/passwd`, byte-for-byte.\n\n## Impact\n\nAn authenticated uploader can read server-local files and republish them through a public GIF media URL by supplying a crafted same-origin `/videos/...` path to `downloadURL_gifimage`. Because traversal scrubbing was bypassable and the fetched bytes were written to the GIF destination without effective invalid-image cleanup, successful exploitation allows disclosure of files such as `/etc/passwd`, readable application source code, or deployment-specific configuration accessible to the application.\n\n\n## Recommended fix\n\n- Reject any remote image URL whose decoded path contains traversal markers\n- Do not allow attacker-controlled same-origin `/videos/...` fetches to resolve into local file reads\n- Constrain any local shortcut path handling with `realpath()` and strict base-directory allowlists\n- Validate GIF content before saving it into public media storage\n- Ensure invalid-image cleanup checks the correct destination path",
  "severity" : [ {
    "type" : "CVSS_V3",
    "score" : "CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:L/A:L"
  } ],
  "affected" : [ {
    "package" : {
      "ecosystem" : "Packagist",
      "name" : "WWBN/AVideo"
    },
    "ranges" : [ {
      "type" : "ECOSYSTEM",
      "events" : [ {
        "introduced" : "0"
      }, {
        "last_affected" : "26.0"
      } ]
    } ]
  } ],
  "references" : [ {
    "type" : "WEB",
    "url" : "https://github.com/WWBN/AVideo/security/advisories/GHSA-f4f9-627c-jh33"
  }, {
    "type" : "ADVISORY",
    "url" : "https://nvd.nist.gov/vuln/detail/CVE-2026-39369"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/WWBN/AVideo/commit/2375eb5e0a6d3cbcfb05377657d0820a7d470b1d"
  }, {
    "type" : "PACKAGE",
    "url" : "https://github.com/WWBN/AVideo"
  } ],
  "database_specific" : {
    "cwe_ids" : [ "CWE-22" ],
    "severity" : "HIGH",
    "github_reviewed" : true,
    "github_reviewed_at" : "2026-04-08T00:08:44Z",
    "nvd_published_at" : "2026-04-07T20:16:31Z"
  }
}