Is CVE-2021-39191 in the CISA KEV catalog?

No. CVE-2021-39191 is not currently on the CISA Known Exploited Vulnerabilities list.

What is the CVSS severity of CVE-2021-39191?

CVE-2021-39191 has a CVSS v3 base score of 4.7 (MEDIUM).

What is the EPSS score for CVE-2021-39191?

CVE-2021-39191 has an EPSS score of 1.75% (75th percentile), estimating the probability of exploitation in the next 30 days.

How do I fix CVE-2021-39191?

Upgrade libapache2-mod-auth-openidc on debian 11 to 2.4.9.4-0+deb11u1 or later.

CVE & CISA-KEV Catalog

CVE-2021-39191

MEDIUMEPSS 75th pctl

4.7

CVSS v3

NVD

Description

mod_auth_openidc is an authentication/authorization module for the Apache 2.x HTTP server that functions as an OpenID Connect Relying Party, authenticating users against an OpenID Connect Provider. In versions prior to 2.4.9.4, the 3rd-party init SSO functionality of mod_auth_openidc was reported to be vulnerable to an open redirect attack by supplying a crafted URL in the `target_link_uri` parameter. A patch in version 2.4.9.4 made it so that the `OIDCRedirectURLsAllowed` setting must be applied to the `target_link_uri` parameter. There are no known workarounds aside from upgrading to a patched version.

CWE-601Open Redirect

How to fix

Remediation Available

libapache2-mod-auth-openidcDebian

Fixed in:2.4.9.4-0+deb11u1CVE-2021-39191

Fixed in:2.4.9.4-1CVE-2021-39191

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 RequiredNone

User InteractionRequired

ScopeChanged

Impact

ConfidentialityNone

IntegrityLow

AvailabilityNone

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

Exploit Intelligence

1.75%probability of exploitation in 30 days

75thpercentile

Elevated risk: more likely to be exploited than 75% of all known CVEs.

References

Patch1

github.com

Exploit1

github.com

Vendor Advisory1

github.com

Mailing List1

lists.debian.org

Release Notes1

github.com

Other references2

Related Vulnerabilities

Other CWE-601 (Open Redirect) vulnerabilities, ordered by exploit likelihood. View all

CVE	Severity	CVSS	EPSS	Exploited	Fix
CVE-2025-4123	High	7.6	98%	-	Fix
CVE-2018-11784	Medium	4.3	94%	-	Fix
CVE-2021-22881	Medium	6.1	87%	-	Fix
CVE-2022-45402	Medium	6.1	82%	-	Fix
CVE-2017-1000117	High	8.8	78%	-	Fix
CVE-2019-10098	Medium	6.1	74%	-	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 2024-11-21.