FFmpeg CVE-2026-120210

Exploitation requires that the target open or demux an attacker-controlled IMF (Interoperable Master Format) package using FFmpeg's IMF demuxer, where the ASSETMAP XML contains Path elements with '..' sequences or absolute paths that are not validated against the package root. The concrete limiting factors are: passive user interaction / ingestion is required (UI:P) - the package must be processed, so there is no fully autonomous remote trigger; impact is restricted to reading file existence and size and to issuing server-side requests (VC:L), with no write/integrity or availability impact; and the affected code path is only reached when the IMF demuxer is actually invoked on the malicious input. Highest real-world exposure is in automated server-side media-ingestion/transcoding services that accept untrusted IMF packages.

This is a medium-severity information-disclosure/SSRF issue, not an emergency. The CVSS 4.0 vector (AV:N/AC:L/AT:N/PR:N/UI:P/VC:L, score 5.3) indicates network reach and low complexity with no privileges, but it is gated by passive user interaction (UI:P) - a victim must process an attacker-supplied IMF package - and the impact is confined to low confidentiality (VC:L) with no integrity or availability effect (VI:N/VA:N) and no scope change (SC:N). No CISA KEV listing and no EPSS score were provided, and no exploit/PoC reference is present in the input, so exploitation appears theoretical at this time; the vuln.today decision label is 'this_month', consistent with a real but non-urgent priority. The practical risk is limited to probing local file existence/size and coercing server-side requests (SSRF) - valuable in multi-tenant or server-side media-processing pipelines (e.g., transcoding services that ingest untrusted IMF packages) but far below arbitrary code execution. Treat as a patch-this-cycle issue rather than a drop-everything one.

A server-side media pipeline (or a user) ingests an attacker-crafted IMF package whose ASSETMAP Path elements contain '..' or absolute paths. When FFmpeg's IMF demuxer resolves those paths, it opens files outside the package directory, letting the attacker confirm the existence and size of local files or force the host to issue outbound (server-side) requests. No public exploit identified at time of analysis; the only exploitation gate is getting the target to demux the malicious package.