What is CVE-2021-20308?

CVE-2021-20308 is a critical-severity vulnerability in Htmldoc Project, classified under Integer Overflow or Wraparound. CVSS score: 9.8/10. Published 2021-04-05.

How severe is CVE-2021-20308?

Critical severity. CVSS v3 base score is 9.8 out of 10.

Integer overflow in Htmldoc Project

CVE-2021-20308

Integer overflow in the htmldoc 1.9.11 and before may allow attackers to execute arbitrary code and cause a denial of service that is similar to CVE-2017-9181.

Vulnerability class: Integer Overflow

Published 2021-04-05 · last modified 2026-06-17.

CVSS v3 metric

CVSS v3 base score 9.8 (Critical). Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H.

EPSS exploit prediction

EPSS: 0.025 (84.0th percentile), scored 2026-10-01.

Low probability of exploitation in the next 30 days, but still tracked. 84th percentile — 84.0% of CVEs in the catalogue have a lower EPSS than this one. How to read EPSS.

EPSS over last 30 days · oldest: 0.025 · newest: 0.025 · change: 0.000

Affected products

Htmldoc Project
Debian Linux — versions 9.0
Htmldoc — versions htmldoc 1.9.11 and older

Weakness classification (CWE)

CWE-190 — Integer Overflow or Wraparound

References

github.com/michaelrsweet/htmldoc/issues/423 (Exploit, Third Party Advisory, Issue Tracking)
bugzilla.redhat.com/show_bug.cgi (Exploit, Third Party Advisory, Issue Tracking)
lists.debian.org/debian-lts-announce/2021/07/msg00000.html (mailing-list, Mailing List, Third Party Advisory)

Frequently asked questions

What is CVE-2021-20308?: CVE-2021-20308 is a critical-severity vulnerability in Htmldoc Project, classified under Integer Overflow or Wraparound. CVSS score: 9.8/10. Published 2021-04-05.
How severe is CVE-2021-20308?: Critical severity. CVSS v3 base score is 9.8 out of 10.