What is CVE-2021-42204?

CVE-2021-42204 is a high-severity vulnerability in Swftools, classified under Out-of-bounds Write. CVSS score: 7.8/10. Published 2022-06-02.

How severe is CVE-2021-42204?

High severity. CVSS v3 base score is 7.8 out of 10.

Buffer overflow in Swftools

CVE-2021-42204

An issue was discovered in swftools through 20201222. A heap-buffer-overflow exists in the function swf_GetBits() located in rfxswf.c. It allows an attacker to cause code execution.

Vulnerability class: Buffer Overflow

Published 2022-06-02 · last modified 2026-06-17.

CVSS v3 metric

CVSS v3 base score 7.8 (High). Vector: CVSS:3.1/AV:L/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H.

EPSS exploit prediction

EPSS: 0.013 (68.7th percentile), scored 2026-09-29.

Low probability of exploitation in the next 30 days, but still tracked. 69th percentile — 68.7% of CVEs in the catalogue have a lower EPSS than this one. How to read EPSS.

EPSS over last 30 days · oldest: 0.013 · newest: 0.013 · change: 0.000

Affected products

Swftools

Weakness classification (CWE)

CWE-787 — Out-of-bounds Write

References

github.com/matthiaskramm/swftools/issues/169 (Exploit, Third Party Advisory)

Frequently asked questions

What is CVE-2021-42204?: CVE-2021-42204 is a high-severity vulnerability in Swftools, classified under Out-of-bounds Write. CVSS score: 7.8/10. Published 2022-06-02.
How severe is CVE-2021-42204?: High severity. CVSS v3 base score is 7.8 out of 10.