Out-of-bounds write via overflowed CENC size check
Published Apr 16, 2026 · Updated Apr 16, 2026
Integer overflow in FFmpeg before 8.1 allows local users to trigger an out-of-bounds write via crafted CENC subsample data. The cenc_scheme_decrypt, cbc1_scheme_decrypt, cens_scheme_decrypt, and cbcs_scheme_decrypt checks add clear and protected byte counts at insufficient width, allowing the sum to wrap below the remaining packet size. Processing a malformed encrypted MOV or MP4 input is required; the wrapped length lets decryption write beyond the packet buffer, corrupting process memory or crashing FFmpeg.
Summary
What happened
Integer overflow in FFmpeg before 8.1 allows local users to trigger an out-of-bounds write via crafted CENC subsample data. The cenc_scheme_decrypt, cbc1_scheme_decrypt, cens_scheme_decrypt, and cbcs_scheme_decrypt checks add clear and protected byte counts at insufficient width, allowing the sum to wrap below the remaining packet size. Processing a malformed encrypted MOV or MP4 input is required; the wrapped length lets decryption write beyond the packet buffer, corrupting process memory or crashing FFmpeg.
The record
- CVE
- CVE-2026-40962
- Published
- Apr 16, 2026
- Updated
- Apr 16, 2026
- Vendor
- FFmpeg
- Product
- FFmpeg
- Classifications
- CWE-190
- Attack vector
- local
- Privileges
- unauthenticated
Timeline
How it unfolded
- Apr 16, 2026CVE publishedPublication date reported by the CVE source.
- Apr 16, 2026Record updatedLatest update available in the CVE record.
Exploitability
Present is not the same as exploitable
Compare your product and version with the public record. A matching version still requires validation against your environment.
Is a vulnerable build present?
Compare these published version ranges with your installed build and any vendor patches.
- Affected versionversion=4.1 <8.1
What conditions does exploitation require?
What is affected?
Attacks
What attackers are doing with it
Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.
Weakness, pattern, technique
Public exploit references
No public exploit references are available in this record.
Labels summarize the accepted research assessment. They do not indicate a test against your environment.
Technologies
Your stack
See the directory against your own environment.
Your stack
Check the software in your environment
Book a demo to see how Hinoki identifies affected software and validates exploitability in your environment.
Book a demo