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Fencer Vulns
critical 9.8

CVE-2021-20308 json

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 simil…

published 2021-04-05 5 y ago modified 2026-06-17 4 mo ago also EUVD-2021-7733

cvss
9.8
version 3.1, NVD
cisa kev
Not listed
not in CISA's catalog
epss
2.5%
EPSS 2.5% chance of exploitation in 30 days, percentile 84%
public exploits
0
none known

Summary

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.

Patch / fix

  • htmldoc Debian 14, Debian 13, Debian 12 1.9.11-3

debian advisories DEBIAN-CVE-2021-20308

  • htmldoc Ubuntu Pro 14.04 LTS 1.8.27-8ubuntu1+esm3
  • htmldoc Ubuntu Pro 16.04 LTS 1.8.27-8ubuntu1.1+esm2
  • htmldoc Ubuntu Pro 18.04 LTS 1.9.2-1ubuntu0.2+esm1
  • htmldoc Ubuntu Pro 20.04 LTS 1.9.7-1ubuntu0.3+esm1

ubuntu advisories UBUNTU-CVE-2021-20308

Ubuntu security data © Canonical Ltd., from https://github.com/canonical/ubuntu-security-notices via OSV; changed: normalised to fixed package versions per release. CC BY-SA 4.0

  • htmldoc Subscription Management Tool 11 SP3 1.8.27-170.4.9.1

suse advisories SUSE-SU-2022:14898-1

  • htmldoc openSUSE Tumbleweed 1.9.12-1.2
  • htmldoc Package Hub 12 SP1 1.8.28-6.1
  • htmldoc Package Hub 15 SP1 1.9.12-bp151.4.3.1
  • htmldoc Package Hub 15 SP2 1.9.12-bp152.4.3.1
  • htmldoc openSUSE Leap 15.2 1.9.12-lp152.4.3.1

opensuse advisories openSUSE-SU-2024:10848-1openSUSE-SU-2021:1266-1openSUSE-SU-2021:0895-1openSUSE-SU-2021:0893-1openSUSE-SU-2021:0882-1

  • htmldoc Arch Linux 1.9.12-1

arch linux advisories AVG-1773

Vendor advisories

What the vendors themselves say about their products: affected, fixed or not affected, and what to do.

red hat product security vex CVE-2021-20308 updated cvss 4.7

htmldoc: Integer overflow in image_load_gif()

  • Red Hat All currently supported Red Hat products
    not affected: vulnerable code not present

Red Hat CSAF VEX © Red Hat, Inc., from https://security.access.redhat.com/data/csaf/v2/vex/; changed: reduced to product statuses and remediations. CC BY 4.0 · csaf

Exploit prediction

2.48% chance of exploitation in the next 30 days, higher than 84% of all scored CVEs (FIRST EPSS, 2026-11-08).

Exploits and checks

  • github.com https://github.com/michaelrsweet/htmldoc/issues/423 referenced PoC, tagged "exploit" by a source, unverified
  • bugzilla.redhat.com https://bugzilla.redhat.com/show_bug.cgi?id=1946289 referenced PoC, tagged "exploit" by a source, unverified

CVSS scores

assigned by version score vector
NVD 3.1 9.8 CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
NVD 2.0 7.5 AV:N/AC:L/Au:N/C:P/I:P/A:P

Affected products

  • n/a htmldoc

Classification

Weakness
  • CWE-190 Integer Overflow or Wraparound

References

Sources

Fencer Vulns keeps one entry per vulnerability: the CVE id wins, then GHSA, and records that alias each other are merged, except that two CVEs always keep separate entries. The same data is available as JSON.