CVE-2019-9718 — In FFmpeg 3

In FFmpeg 3.2 and 4.1, a denial of service in the subtitle decoder allows attackers to hog the CPU via a crafted video file in Matroska format, because ff_htmlmarkup_to_ass in libavcodec/htmlsubtitles.c has a complex format argument to sscanf.

01What is this vulnerability?

In FFmpeg 3.2 and 4.1, a denial of service in the subtitle decoder allows attackers to hog the CPU via a crafted video file in Matroska format, because ff_htmlmarkup_to_ass in libavcodec/htmlsubtitles.c has a complex format argument to sscanf.

02Affected products

Vendor	Product	Versions
n	a / n/a	n/a

03Active exploitation status

Not currently listed on the CISA Known Exploited Vulnerabilities (KEV) catalog. EPSS is the best forward-looking signal — see the EPSS row above.

04Recommended remediation

• Patch to a fixed version listed in the vendor advisory (see references below).
• Mitigate with WAF rules, network egress filters, or feature flags where the patch is not yet available.
• Hunt historical logs for exploitation indicators — see Detection signatures below.

05Technical details

For the full vendor write-up, exploit chains, and reference implementations, see the references list in section 09.

06Detection signatures

Ask SARA in chat to draft a starting detection for this CVE in your stack of choice.

07Related CVEs

No directly-cited follow-up CVEs in the KB record for this advisory. The references list in section 09 carries the vendor cross-references.

08Timeline

• Published: 2019-03-12T06:00:00.000Z
• Last modified: 2024-08-04T22:01:53.269Z

09References

• git.ffmpeg.org — https://git.ffmpeg.org/gitweb/ffmpeg.git/commit/1f00c97bc3475c477f3c468cf2d924d5…
• www.securityfocus.com — http://www.securityfocus.com/bid/107382
• usn.ubuntu.com — https://usn.ubuntu.com/3967-1/
• seclists.org — https://seclists.org/bugtraq/2019/May/60
• www.debian.org — https://www.debian.org/security/2019/dsa-4449
• github.com — https://github.com/FFmpeg/FFmpeg/commit/23ccf3cabb4baf6e8af4b1af3fcc59c904736f21