How severe is CVE-2019-9721?

CVE-2019-9721 has a CVSS 3.x base score of 6.5, rated medium severity. It is exploitable over network with low attack complexity, requires no privileges and user interaction. Impact on confidentiality is none, integrity none, and availability high.

Is CVE-2019-9721 being actively exploited?

It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 1% (70th percentile), an estimate of the probability of exploitation in the next 30 days.

What products are affected by CVE-2019-9721?

CVE-2019-9721 primarily affects Ffmpeg. In total, 5 product configurations (CPEs) are listed as vulnerable; see the affected-products list for the exact versions.

How do I fix CVE-2019-9721?

Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround.

When was CVE-2019-9721 published?

CVE-2019-9721 was published on 2019-03-12 and last updated on 2026-06-17.

CVE-2019-9721

CVE-2019-9721 is a medium-severity vulnerability in Ffmpeg with a CVSS 3.x base score of 6.5. It is not currently listed as actively exploited by CISA, and its EPSS exploit-prediction score is low. The underlying weakness is classified as CWE-125.

Key facts

Severity: Medium (CVSS 3.x base score 6.5)
CVSS v2: 4.3
EPSS exploit prediction: 1% (70th percentile)
Actively exploited: Not listed in CISA KEV
Weakness: CWE-125
Affected product: Ffmpeg
Published: 2019-03-12
Last modified: 2026-06-17

Description

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

Frequently asked questions

What is CVE-2019-9721?: A denial of service in the subtitle decoder in FFmpeg 3.2 and 4.1 allows attackers to hog the CPU via a crafted video file in Matroska format, because handle_open_brace in libavcodec/htmlsubtitles.c has a complex format argument to sscanf.
How severe is CVE-2019-9721?: CVE-2019-9721 has a CVSS 3.x base score of 6.5, rated medium severity. It is exploitable over network with low attack complexity, requires no privileges and user interaction. Impact on confidentiality is none, integrity none, and availability high.
Is CVE-2019-9721 being actively exploited?: It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 1% (70th percentile), an estimate of the probability of exploitation in the next 30 days.
What products are affected by CVE-2019-9721?: CVE-2019-9721 primarily affects Ffmpeg. In total, 5 product configurations (CPEs) are listed as vulnerable; see the affected-products list for the exact versions.
How do I fix CVE-2019-9721?: Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround.
When was CVE-2019-9721 published?: CVE-2019-9721 was published on 2019-03-12 and last updated on 2026-06-17.

References

Affected products (5)

cpe:2.3:a:ffmpeg:ffmpeg:3.2:*:*:*:*:*:*:*
cpe:2.3:a:ffmpeg:ffmpeg:4.1:*:*:*:*:*:*:*
cpe:2.3:o:canonical:ubuntu_linux:18.04:*:*:*:lts:*:*:*
cpe:2.3:o:canonical:ubuntu_linux:18.10:*:*:*:*:*:*:*
cpe:2.3:o:canonical:ubuntu_linux:19.04:*:*:*:*:*:*:*

More vulnerabilities in Ffmpeg

CVE-2013-0864 — Critical (CVSS 10.0): The gif_copy_img_rect function in libavcodec/gifdec.c in FFmpeg before 1.1.2 performs an incorrect calculation for an…
CVE-2013-4265 — Critical (CVSS 10.0): The av_reallocp_array function in libavutil/mem.c in FFmpeg before 2.0.1 has an unspecified impact and remote vectors…
CVE-2013-0873 — Critical (CVSS 10.0): The read_header function in libavcodec/shorten.c in FFmpeg before 1.1.3 allows remote attackers to have an unspecified…
CVE-2013-0872 — Critical (CVSS 10.0): The swr_init function in libswresample/swresample.c in FFmpeg before 1.1.3 allows remote attackers to have an…
CVE-2011-3937 — Critical (CVSS 10.0): The H.263 codec (libavcodec/h263dec.c) in FFmpeg 0.7.x before 0.7.12, 0.8.x before 0.8.11, and unspecified versions…
CVE-2012-2804 — Critical (CVSS 10.0): Unspecified vulnerability in libavcodec/indeo3.c in FFmpeg before 0.11 and Libav 0.8.x before 0.8.5 has unknown impact…

All CVEs affecting Ffmpeg →

Other CWE-125 (Out-of-bounds Read) vulnerabilities

CVE-2026-24826 — Critical (CVSS 10.0): Out-of-bounds Write, Divide By Zero, NULL Pointer Dereference, Use of Uninitialized Resource, Out-of-bounds Read,…
CVE-2024-22004 — Critical (CVSS 10.0): Due to length check, an attacker with privilege access on a Linux Nonsecure operating system can trigger a…
CVE-2021-41556 — Critical (CVSS 10.0): sqclass.cpp in Squirrel through 2.2.5 and 3.x through 3.1 allows an out-of-bounds read (in the core interpreter) that…
CVE-2021-21777 — Critical (CVSS 10.0): An information disclosure vulnerability exists in the Ethernet/IP UDP handler functionality of EIP Stack Group OpENer…
CVE-2017-14451 — Critical (CVSS 10.0): An exploitable out-of-bounds read vulnerability exists in libevm (Ethereum Virtual Machine) of CPP-Ethereum. A…
CVE-2013-0767 — Critical (CVSS 10.0): The nsSVGPathElement::GetPathLengthScale function in Mozilla Firefox before 18.0, Firefox ESR 10.x before 10.0.12 and…

Browse all CWE-125 (Out-of-bounds Read) vulnerabilities →