CVE-2026-107697: 
Ffmpeg vulnerability analysis and mitigation

CVE-2026-107697 is a protection mechanism failure in FFmpeg's HLS (HTTP Live Streaming) demuxer that allows attackers to bypass protocol whitelist and allowed_extensions restrictions when opening child playlists. All FFmpeg versions before 8.1.3 are affected. The vulnerability was disclosed on October 8, 2026, with patches available in the same timeframe. It carries a CVSS v3.1 base score of 4.3 (Medium) and a CVSS v4.0 base score of 5.3 (Medium) (GitHub Advisory, VulnCheck).

The root cause is classified as CWE-693 (Protection Mechanism Failure) and CWE-641 (Improper Restriction of Names for Files and Other Resources). In libavformat/hls.c, the parse_playlist() function's code path for opening a new child playlist (when in == NULL) directly called c->ctx->io_open(), bypassing the protocol whitelist and file-extension checks enforced by the open_url() function. This allowed child playlist URLs referenced in a master playlist to use protocols other than the permitted file, http, or data schemes, or to reference files with disallowed extensions. The fix routes the affected branch through open_url() so all child playlists are subject to the same security policy as segment URLs (FFmpeg Commit 23602df, FFmpeg Source n8.1.2).

Successful exploitation allows an unauthenticated attacker to bypass HLS security policy, enabling access to local files and resources via disallowed protocols that should be blocked by the demuxer. The primary impact is a confidentiality breach (low severity), as an attacker can cause FFmpeg to read non-multimedia local files or use restricted protocols. There is no integrity or availability impact. Exploitation requires user interaction — a victim must open a crafted HLS master playlist (VulnCheck, GitHub Advisory).

There is no public proof-of-concept exploit and no evidence of in-the-wild exploitation at the time of disclosure (VulnCheck). The vulnerability is not listed in the CISA Known Exploited Vulnerabilities (KEV) catalog. The EPSS score is approximately 0.324%, indicating a low probability of exploitation in the near term. No threat actor attribution has been reported. The vulnerability was discovered by researcher "depthfirst" (FFmpeg Commit 23602df).

1. Craft a malicious HLS master playlist: Create an M3U8 master playlist file that references child playlists using disallowed protocols (e.g., ftp://, rtmp://, or arbitrary local file paths with non-multimedia extensions such as /etc/passwd).
2. Host or deliver the playlist: Host the crafted master playlist on an attacker-controlled web server, or deliver it via social engineering (e.g., a malicious link, email attachment, or embedded media player).
3. Induce victim to open the playlist: Trick a user into opening the malicious master playlist with a vulnerable FFmpeg installation (version < 8.1.3), for example via ffplay malicious.m3u8 or through an application that uses FFmpeg for media processing.
4. Trigger the bypass: When FFmpeg's HLS demuxer processes the master playlist and encounters a child playlist entry (in == NULL path), parse_playlist() calls c->ctx->io_open() directly, bypassing open_url() security checks, and opens the disallowed resource.
5. Exfiltrate data: The contents of the accessed local file or disallowed-protocol resource may be processed or exposed through FFmpeg's output, error messages, or network callbacks, potentially leaking sensitive information (FFmpeg Commit 23602df, VulnCheck).

• Network: Unexpected outbound connections from FFmpeg processes to non-HTTP/HTTPS protocols (e.g., FTP, RTMP) or unusual destinations when processing HLS streams; FFmpeg processes initiating connections to internal network resources.
• File System: FFmpeg processes accessing non-multimedia files (e.g., /etc/passwd, /etc/shadow, configuration files) as detected by file access auditing (e.g., auditd on Linux).
• Logs: Application or system logs showing FFmpeg opening files with unexpected extensions or protocols; error messages referencing unusual URLs in HLS playlist processing.
• Process: FFmpeg or media player processes spawned with HLS playlist arguments pointing to local file paths or non-standard protocol URLs.

Upgrade FFmpeg to version 8.1.3 or later, which routes child playlist URL opening through open_url() to enforce protocol and extension security checks (FFmpeg Commit 23602df, GitHub Advisory). As a workaround prior to patching, restrict users from opening HLS playlists from untrusted sources, and implement network-level controls to limit the protocols FFmpeg can access. Additionally, consider using FFmpeg's -allowed_extensions and -protocol_whitelist options to explicitly restrict permitted protocols and file extensions when processing HLS content from untrusted inputs (VulnCheck).