CVE-2021-26539

Exp

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.

Published: 2021-02-08 Last update: 2026-06-16 Assigner: [email protected] Source: [email protected]
NVD Status：Modified，CVE State: published
View at NVD, CVE.org, EUVD

CVE-2021-26539 is rated High Exploit Risk (65/100): CVSS Medium severity, with medium exploitation likelihood (EPSS 1.95%). 1 public exploit reference(s) are indexed (Exploit-DB). EPSS rose +1.66% over the last day, indicating growing attacker interest. Public exploits are available—assess exposure, apply mitigations, and prioritize patching.

Risk is dynamic; we continuously reassess and refresh what is shown on this page as upstream context changes.

Public exploit references (Exploit-DB) for CVE-2021-26539

EDB-ID Source Kind Published Link
— nvd_ref exploit_tag Exploit-DB ↗

Exploit prediction scoring system (EPSS) score for CVE-2021-26539

EPSS lead: Daily EPSS estimates relative likelihood of exploitation; percentile ranks this CVE among scored vulnerabilities (higher = more severe relative rank).

# Date Old EPSS score New EPSS score Delta (New - Old)
1 2026-06-15 0.29% 1.95% +1.66%
2 2025-04-28 0.21% 0.29% +0.08%
3 2025-03-30 — 0.21% —

Full EPSS history (10 records total)

Common vulnerability scoring system (CVSS) metrics for CVE-2021-26539

CVSS metrics for this CVE.

Base score Version Severity Vector Exploitability Impact Score source
5.3 3.1 MEDIUM
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:N Click to expand
Attack vector (AV:N)
Could be attacked over the internet or any normal routed network—not just someone sitting at the machine.
Attack complexity (AC:L)
Once they can reach the bug, pulling it off is straightforward—no weird race conditions or rare setup.
Privileges required (PR:N)
No account or special rights needed—anonymous or random user is enough.
User interaction (UI:N)
Nobody has to click “OK” or open a trap file; it can work without a victim helping.
Scope (S:U)
Damage stays in the same “trust bubble” as the broken component—no big spill into unrelated systems.
Confidentiality (C:N)
Doesn’t really leak secrets in a meaningful way.
Integrity (I:L)
Attackers could change some data, but it’s limited—not everything goes.
Availability (A:N)
Service keeps running; no real outage angle.
 3.9 1.4 [email protected]
5.0 2.0 MEDIUM
AV:N/AC:L/Au:N/C:N/I:P/A:N Click to expand
Access vector (AV:N)
Can be exploited remotely over network reachability.
Access complexity (AC:L)
Exploitation conditions are straightforward and predictable.
Authentication (AU:N)
No authentication is required.
Confidentiality impact (C:N)
No confidentiality impact.
Integrity impact (I:P)
Partial integrity impact.
Availability impact (A:N)
No availability impact.
 10.0 2.9 [email protected]

Weakness enumeration for CVE-2021-26539

GitHub Security Advisory for CVE-2021-26539

GHSA-rjqq-98f6-6j3r · Severity: medium · Ecosystem: npm — Improper Input Validation in sanitize-html

OS Trackers for CVE-2021-26539

vendor priority summary link
debian unimportant CVE-2021-26539 unimportant priority: Debian including 1 source packages (node-sanitize-html), 4 status rows across 4 suites (bookworm, forky, sid, trixie): resolved 4. https://security-tracker.debian.org/tracker/CVE-2021-26539
redhat medium — https://access.redhat.com/security/cve/CVE-2021-26539

Affected software / configurations for CVE-2021-26539

Vendor Product Version Raw CPE
apostrophecms sanitize-html < 2.3.1 cpe:2.3:a:apostrophecms:sanitize-html:*:*:*:*:*:node.js:*:*

References for CVE-2021-26539

cvelogic Threat Intelligence