{"id":"GHSA-f4f9-627c-jh33","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","aliases":["CVE-2026-39369"],"modified":"2026-09-10T03:50:44.094304555Z","published":"2026-04-08T00:08:44Z","related":["CVE-2026-41062"],"database_specific":{"severity":"HIGH","github_reviewed":true,"github_reviewed_at":"2026-04-08T00:08:44Z","nvd_published_at":"2026-04-07T20:16:31Z","cwe_ids":["CWE-22"]},"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"}],"affected":[{"package":{"name":"WWBN/AVideo","ecosystem":"Packagist","purl":"pkg:composer/WWBN/AVideo"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"last_affected":"26.0"}]}],"database_specific":{"source":"https://github.com/github/advisory-database/blob/main/advisories/github-reviewed/2026/04/GHSA-f4f9-627c-jh33/GHSA-f4f9-627c-jh33.json"}}],"schema_version":"1.9.0","severity":[{"type":"CVSS_V3","score":"CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:L/A:L"}]}