PatchSiren cyber security CVE debrief
CVE-2026-64830 FFmpeg CVE debrief
CVE-2026-64830 is a heap buffer overflow vulnerability in FFmpeg versions 2.1 through 8.1.2. The vulnerability exists in the VobSub subtitle demuxer and allows attackers to corrupt adjacent heap memory by supplying a malicious .sub/.idx subtitle file declaring more distinct stream IDs than the fixed-size array bounds in libavformat/mpeg.c. Attackers can craft a subtitle file with excessive distinct stream IDs to trigger unbounded writes beyond the vobsub->q[] array boundary via ff_subtitles_queue_insert(), potentially achieving arbitrary code execution in any application using FFmpeg's VobSub demuxer.
- Vendor
- FFmpeg
- Product
- Unknown
- CVSS
- HIGH 8.7
- CISA KEV
- Not listed in stored evidence
- Original CVE published
- 2026-07-22
- Original CVE updated
- 2026-07-22
- Advisory published
- 2026-07-22
- Advisory updated
- 2026-07-22
Who should care
Users and organizations that utilize FFmpeg's VobSub subtitle demuxer in their applications or services should be aware of this vulnerability. This includes developers, system administrators, and security professionals responsible for maintaining and securing software that incorporates FFmpeg.
Technical summary
The vulnerability is caused by a lack of bounds checking in the VobSub subtitle demuxer when processing .sub/.idx subtitle files. Specifically, the demuxer does not properly validate the number of distinct stream IDs in the file, allowing attackers to craft malicious files that trigger a heap buffer overflow. This can lead to arbitrary code execution in applications that use FFmpeg's VobSub demuxer.
Defensive priority
High
Recommended defensive actions
- Update FFmpeg to version 8.1.3 or later
- Implement input validation and sanitization for .sub/.idx subtitle files
- Use a memory corruption prevention mechanism, such as Address Space Layout Randomization (ASLR) and Data Execution Prevention (DEP)
- Monitor for suspicious activity and implement logging and auditing mechanisms
- Perform a thorough review of the system configuration and architecture to identify potential vulnerabilities
- Conduct regular security audits and vulnerability assessments to identify and address potential weaknesses
- Implement a robust incident response plan to quickly respond to and contain potential security incidents
Evidence notes
The CVE record was published on 2026-07-22T17:16:58.557Z and has not been modified since then. The NVD entry is currently Undergoing Analysis. The vulnerability was disclosed by VulnCheck via multiple references, including a commit and a pull request on the FFmpeg Git repository, as well as an advisory on their website.
Official resources
AI-assisted PatchSiren debrief based on the supplied source corpus. The CVE record was published on 2026-07-22T17:16:58.557Z and has not been modified since then. The NVD entry is currently Undergoing Analysis.