Null pointer dereference in the htmldoc v1.9.11 and before may allow attackers to execute arbitrary code and cause a denial of service via…

published 2022-03-03 4 y ago modified 2026-06-17 4 mo ago also EUVD-2021-13730

cvss: 7.8; version 3.1, NVD
cisa kev: Not listed; not in CISA's catalog
epss: 0.8%; EPSS 0.8% chance of exploitation in 30 days, percentile 58%
public exploits: 0; none known

Null pointer dereference in the htmldoc v1.9.11 and before may allow attackers to execute arbitrary code and cause a denial of service via a crafted html file.

Patch / fix

distros 3 links 1

debian ubuntu arch linux

htmldoc Debian 14, Debian 13, Debian 12 1.9.11-4

debian advisories DEBIAN-CVE-2021-26948

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-2021-26948

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 Arch Linux 1.9.12-1

arch linux advisories AVG-1773

github.com/michaelrsweet/htmldoc/issues/410 advisory

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-2021-26948 updated 2025-11-21 cvss 5.3

htmldoc: null pointer dereference in copy_image()

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

0.84% chance of exploitation in the next 30 days, higher than 58% of all scored CVEs (FIRST EPSS, 2026-11-08).

Exploits and checks

github.com https://github.com/michaelrsweet/htmldoc/issues/410 referenced PoC, tagged "exploit" by a source, unverified

CVSS scores

assigned by	version	score	vector
NVD	3.1	7.8	CVSS:3.1/AV:L/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H
NVD	2.0	6.8	AV:N/AC:M/Au:N/C:P/I:P/A:P

Affected products

n/a htmldoc

Classification

Weakness

CWE-479 Signal Handler Use of a Non-reentrant Function
CWE-476 NULL Pointer Dereference

References

github.com /michaelrsweet/htmldoc/issues/410
exploit, issue-tracking, patch, third-party-advisory

Sources

CVE List CVE-2021-26948
NVD CVE-2021-26948

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.

Summary