CVE-2026-66039
Signed integer overflow in FFmpeg MACE6 decoder allows heap corruption and potential RCE.
Is CVE-2026-66039 being exploited?
Not confirmed. CVE-2026-66039 does not appear in CISA's Known Exploited Vulnerabilities catalog, which records only exploitation that has been observed and reported publicly. That is evidence of absence of a report, not evidence the flaw is unattacked. EPSS currently estimates a 0.31% probability of exploitation in the next 30 days.
How severe is CVE-2026-66039?
CVE-2026-66039 is rated High with a CVSS score of 8.7. Severity describes how bad exploitation would be, not how likely it is: pair it with exploitation evidence before deciding what to patch first.
Is there a patch for CVE-2026-66039?
Yes. A fix has been recorded for CVE-2026-66039. The vendor advisory is the authority on the exact fixed version — apply it from there rather than from a summary.
What does CVE-2026-66039 affect?
CVE-2026-66039 affects FFmpeg <= 8.1.2, Applications using FFmpeg MACE6 decoder (players, transcoders, servers). Confirm the exact affected versions against the vendor advisory before deciding you are exposed.
What should I do about CVE-2026-66039?
Update FFmpeg to the commit/version containing aafb5c6 or apply vendor patch.
Exploitation status reflects CISA's KEV catalog as we last synced it. Check the catalog directly.
Crafted CAF files trigger a signed integer overflow in mace_decode_frame(), causing heap OOB write that can enable remote code execution when parsing media.
Patch when possible
- affected<= 8.1.2
As published in the CVE Program record. A version outside these ranges is not a statement that it is unaffected — vendors sometimes understate a range, and distribution-backported builds carry upstream numbers that do not reflect what was patched into them.