How severe is CVE-2021-26539?

CVE-2021-26539 has a CVSS 3.x base score of 5.3, rated medium severity. It is exploitable over network with low attack complexity, requires no privileges and no user interaction. Impact on confidentiality is none, integrity low, and availability none.

Is CVE-2021-26539 being actively exploited?

It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 2% (78th percentile), an estimate of the probability of exploitation in the next 30 days.

What products are affected by CVE-2021-26539?

CVE-2021-26539 affects Apostrophecms Sanitize-html. See the affected-products list for the exact vulnerable versions.

How do I fix CVE-2021-26539?

Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround.

When was CVE-2021-26539 published?

CVE-2021-26539 was published on 2021-02-08 and last updated on 2026-06-17.

CVE-2021-26539

CVE-2021-26539 is a medium-severity vulnerability in Apostrophecms Sanitize-html with a CVSS 3.x base score of 5.3. It is not currently listed as actively exploited by CISA, and its EPSS exploit-prediction score is low.

Key facts

Severity: Medium (CVSS 3.x base score 5.3)
CVSS v2: 5.0
EPSS exploit prediction: 2% (78th percentile)
Actively exploited: Not listed in CISA KEV
Affected product: Apostrophecms Sanitize-html
Published: 2021-02-08
Last modified: 2026-06-17

Description

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.

Frequently asked questions

What is CVE-2021-26539?: 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.
How severe is CVE-2021-26539?: CVE-2021-26539 has a CVSS 3.x base score of 5.3, rated medium severity. It is exploitable over network with low attack complexity, requires no privileges and no user interaction. Impact on confidentiality is none, integrity low, and availability none.
Is CVE-2021-26539 being actively exploited?: It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 2% (78th percentile), an estimate of the probability of exploitation in the next 30 days.
What products are affected by CVE-2021-26539?: CVE-2021-26539 affects Apostrophecms Sanitize-html. See the affected-products list for the exact vulnerable versions.
How do I fix CVE-2021-26539?: Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround.
When was CVE-2021-26539 published?: CVE-2021-26539 was published on 2021-02-08 and last updated on 2026-06-17.

References

Affected products (1)

cpe:2.3:a:apostrophecms:sanitize-html:*:*:*:*:*:node.js:*:*

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