Is CVE-2026-27166 in the CISA KEV catalog?

No. CVE-2026-27166 is not currently on the CISA Known Exploited Vulnerabilities list.

What is the CVSS severity of CVE-2026-27166?

CVE-2026-27166 has a CVSS v3 base score of 4.1 (MEDIUM).

What is the EPSS score for CVE-2026-27166?

CVE-2026-27166 has an EPSS score of 0.19% (8th percentile), estimating the probability of exploitation in the next 30 days.

How do I fix CVE-2026-27166?

Upgrade discourse to 2026.2.1 or later.

CVE & CISA-KEV Catalog

CVE-2026-27166

MEDIUM

4.1

CVSS v3

NVD

Description

Discourse is an open source discussion platform. Prior to versions 2026.3.0-latest.1, 2026.2.1 and 2026.1.2, insufficient cleanup in the default Codepen allowed iframes value allows an attacker to trick a user into changing the URL of the main page. This issue has been fixed in versions 2026.3.0-latest.1, 2026.2.1 and 2026.1.2. To workaround this issue, remove Codepen from the list of allowed iframes.

CWE-80

How to fix

Remediation Available

discourseNVD

Affected:>= 2026.2.0, < 2026.2.1Fixed in:2026.2.1CVE-2026-27166derived from NVD

Remediation is compiled from vendor and distribution security advisories. Always confirm against the linked source for your exact version and platform.

CVSS v3 Vector

Exploitability

Attack VectorNetwork

Attack ComplexityLow

Privileges RequiredLow

User InteractionRequired

ScopeChanged

Impact

ConfidentialityNone

IntegrityLow

AvailabilityNone

CVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:C/C:N/I:L/A:N

Exploit Intelligence

0.19%probability of exploitation in 30 days

8thpercentile

Low risk: more likely to be exploited than 8% of all known CVEs.

References

Patch1

github.com

Vendor Advisory1

github.com

Related Vulnerabilities

Other CWE-80 vulnerabilities, ordered by exploit likelihood. View all

CVE	Severity	CVSS	EPSS	Exploited	Fix
CVE-2022-21145	Medium	4.8	78%	-	-
CVE-2020-13562	Medium	6.1	78%	-	-
CVE-2020-13965	Medium	6.1	77%	KEV	Fix
CVE-2020-13564	Medium	6.1	76%	-	-
CVE-2020-13563	Medium	6.1	76%	-	-
CVE-2024-4439	High	7.2	71%	-	Fix

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This product uses NVD data but is not endorsed or certified by the NVD. EPSS scores courtesy of FIRST.org (https://www.first.org/epss). Source: CISA KEV Catalog. Data as of 2026-03-25.