Skip to content
Fencer Vulns
medium 5.3

CVE-2021-26539 json

Improper Input Validation in sanitize-html

published 2021-02-08 5 y ago modified 2026-06-17 4 mo ago also GHSA-rjqq-98f6-6j3r , EUVD-2021-1183

cvss
5.3
version 3.1, NVD
cisa kev
Not listed
not in CISA's catalog
epss
2.0%
EPSS 2.0% chance of exploitation in 30 days, percentile 80%
public exploits
0
none known

Summary

Apostrophe Technologies sanitize-html before 2.3.1 does not properly handle internationalized domain name (IDN) which could allow an attacker to bypass hostname whitelist validation set by the "allowedIframeHostnames" option.

Patch / fix

  • npm sanitize-html 2.3.1
  • apostrophecms sanitize-html 2.3.1

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-2021-26539 updated cvss 5.3

sanitize-html: improper handling of internationalized domain name (IDN) can lead to bypass hostname whitelist validation

  • Red Hat OpenShift Service Mesh 2.0 servicemesh-prometheus
    affected: no fix available
  • Red Hat OpenShift Container Platform 4.7 openshift4/ose-console v4.7.0-202102130115.p0
    fixed: vendor fix RHSA-2020:5633
  • Red Hat OpenShift Container Platform 4.8 openshift4/ose-thanos-rhel8 v4.8.0-202106291913.p0.git.c358e96.assembly.stream
    fixed: vendor fix RHSA-2021:2438
  • Red Hat OpenShift Container Platform 4.9 openshift4/ose-prometheus v4.9.0-202109302016.p0.git.3197fa7.assembly.stream
    fixed: vendor fix RHSA-2021:3759
  • Red Hat OpenShift Container Platform 4.7 openshift4/ose-cli v4.7.0-202102130115.p0, openshift4/ose-pod v4.7.0-202102130115.p0, openshift4/ose-etcd v4.7.0-202102130115.p0, openshift4/ose-tests v4.7.0-202102181036.p0, openshift4/ose-coredns v4.7.0-202102130115.p0, openshift4/ose-grafana v4.7.0-202102130115.p0, +129 more Red Hat OpenShift Container Platform 4.8 openshift4/ose-cli v4.8.0-202106291725.p0.git.1077b05.assembly.stream, openshift4/ose-pod v4.8.0-202107161820.p0.git.051ac4f.assembly.stream, openshift4/ose-etcd v4.8.0-202106152230.p0.git.aefa6bf.assembly.stream, openshift4/ose-tests v4.8.0-202107131424.p0.git.0d958c3.assembly.stream, openshift4/ose-console v4.8.0-202107010336.p0.git.188a490.assembly.stream, openshift4/ose-coredns v4.8.0-202106291913.p0.git.642b46e.assembly.stream, +135 more Red Hat OpenShift Container Platform 4.9 openshift4/ose-cli v4.9.0-202109302317.p0.git.96e95ce.assembly.stream, openshift4/ose-pod v4.9.0-202110080828.p0.git.894a78b.assembly.stream, openshift4/ose-etcd v4.9.0-202109302317.p0.git.5c1feaf.assembly.stream, openshift4/ose-console v4.9.0-202110130449.p0.git.8c077e4.assembly.rc.8, openshift4/ose-tests v4.9.0-202110011028.p0.git.6105395.assembly.stream, openshift4/ose-coredns v4.9.0-202109302317.p0.git.3cb11c0.assembly.stream, +141 more
    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

1.98% chance of exploitation in the next 30 days, higher than 80% of all scored CVEs (FIRST EPSS, 2026-11-08).

Exploits and checks

  • advisory.checkmarx.net https://advisory.checkmarx.net/advisory/CX-2021-4308 referenced PoC, tagged "exploit" by a source, unverified

CVSS scores

assigned by version score vector
NVD 3.1 5.3 CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:N
NVD 2.0 5.0 AV:N/AC:L/Au:N/C:N/I:P/A:N
GitHub 3.1 5.3 CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:N

Affected packages

ecosystem package affected fixed in
npm sanitize-html
<2.3.1
2.3.1

Classification

Weakness
  • CWE-20 Improper Input Validation

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.