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NVD / CVE Program· CNA GitHub_M

CVE-2021-39191: URL Redirection to Untrusted Site ('Open Redirect') in mod_auth_openidc

Noroxi assessment

Priority: Monitor (action score 25/100)

  • The sources we track (CISA KEV, Exploit-DB, Metasploit, Nuclei, GitHub) show no public exploit code or exploitation in the wild.
  • Probability of exploitation in the next 30 days: 1.7% (FIRST EPSS); higher than 77.6% of all records.
  • Anyone who can reach it over the internet can trigger it. No account or password is required. A user must open a link or visit a page. No special conditions are required; it is repeatable.
  • Fixed version: cjose (AlmaLinux:8) 0.6.1-2.module_el8.6.0+2868+44838709; cjose-devel (AlmaLinux:8) 0.6.1-2.module_el8.6.0+2868+44838709; mod_auth_openidc (AlmaLinux:8) 2.3.7-11.module_el8.6.0+2868+44838709.

Low priority for now. Upgrade to cjose (AlmaLinux:8) 0.6.1-2.module_el8.6.0+2868+44838709; cjose-devel (AlmaLinux:8) 0.6.1-2.module_el8.6.0+2868+44838709; mod_auth_openidc (AlmaLinux:8) 2.3.7-11.module_el8.6.0+2868+44838709 or later.

Generated automatically from the record's data: CVSS (NVD and CNA), CISA KEV and SSVC, FIRST EPSS, exploit sources, fixed versions. How we calculate it

Primary sources: NVD · CVE.org · FIRST EPSS

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.

MediumCVSS 6.1 · v3.1—No exploit Fix available
Published
Sep 3, 2021
Updated
Jun 17, 2026
EPSS
1.7% · 77th percentile

Report tools

JSON

Action score

25

Monitor

Low priority for now.

CVSS
24 / 40 · 6.1 / 10
CISA KEV
0 / 30 · Not listed
EPSS
1 / 30 · 1.7%

CNA vs NVD score

NVD
6.1
CNA · GitHub_M
4.7
1.4 point gap

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

The score given by the assigning authority versus NVD’s independent score. A gap means the severity is contested.

Get told when this record changes

  • Not in KEV: no record of exploitation in the wild
  • No public exploit code on record
  • A fix has been released

If any of these changes, we'll tell you in the daily email digest.

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When you'll hear from us

  • when it enters CISA KEV
  • when exploit code appears or is weaponized
  • when the record is updated (including a fixed version)
  • when EPSS rises 20 points in a week

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Noroxi analysis

What does it mean in your environment?

The assessment above is generated automatically from the record's data; it doesn't know your environment. Our team verifies on your systems whether this vulnerability is actually exploitable and which mitigation is enough.

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Affected systems

Is your version affected?

Pick the product and type the version you run. It's compared with this record's version ranges in your browser; the version isn't sent anywhere.

VendorProduct
openidcmod auth openidc
fedoraprojectfedora
debiandebian linux

Affected versions

NVD version ranges (for catalog products). Add the product to your stack with a version and matching uses these.

  • debian debian linux10.0
  • fedoraproject fedora35
  • fedoraproject fedora36
  • openidc mod auth openidcbefore 2.4.9.4

Versions reported by the vendor

Affected version ranges reported by the assigning authority (GitHub_M). Independent of NVD's CPE analysis and usually ahead of it.

  • zmartzone mod_auth_openidc

    • <=2.4.9.3affected

Package-level exposure

OSV and GitHub Advisory data: ecosystem, package and range. SBOM matching uses this table.

EcosystemPackageAffected rangeFix
AlmaLinux:8cjosebefore 0.6.1-2.module_el8.6.0+2868+448387090.6.1-2.module_el8.6.0+2868+44838709
AlmaLinux:8cjose-develbefore 0.6.1-2.module_el8.6.0+2868+448387090.6.1-2.module_el8.6.0+2868+44838709
AlmaLinux:8mod_auth_openidcbefore 2.3.7-11.module_el8.6.0+2868+448387092.3.7-11.module_el8.6.0+2868+44838709
Debian:10libapache2-mod-auth-openidcbefore 2.3.10.2-1+deb10u32.3.10.2-1+deb10u3
Debian:12libapache2-mod-auth-openidcbefore 2.4.9.4-12.4.9.4-1
openSUSE:Leap 15.4apache2-mod_auth_openidcbefore 2.3.8-150100.3.22.12.3.8-150100.3.22.1
openSUSE:Leap 15.6apache2-mod_auth_openidcbefore 2.4.17.1-150600.16.14.12.4.17.1-150600.16.14.1
Red Hat:enterprise_linux:8::appstreamcjosebefore 0:0.6.1-2.module+el8+2454+f890a43a0:0.6.1-2.module+el8+2454+f890a43a
Red Hat:enterprise_linux:8::appstreamcjose-debuginfobefore 0:0.6.1-2.module+el8+2454+f890a43a0:0.6.1-2.module+el8+2454+f890a43a
Red Hat:enterprise_linux:8::appstreamcjose-debugsourcebefore 0:0.6.1-2.module+el8+2454+f890a43a0:0.6.1-2.module+el8+2454+f890a43a
Red Hat:enterprise_linux:8::appstreamcjose-develbefore 0:0.6.1-2.module+el8+2454+f890a43a0:0.6.1-2.module+el8+2454+f890a43a
Red Hat:enterprise_linux:8::appstreammod_auth_openidcbefore 0:2.3.7-11.module+el8.6.0+14082+b6f23e950:2.3.7-11.module+el8.6.0+14082+b6f23e95
Red Hat:enterprise_linux:8::appstreammod_auth_openidc-debuginfobefore 0:2.3.7-11.module+el8.6.0+14082+b6f23e950:2.3.7-11.module+el8.6.0+14082+b6f23e95
Red Hat:enterprise_linux:8::appstreammod_auth_openidc-debugsourcebefore 0:2.3.7-11.module+el8.6.0+14082+b6f23e950:2.3.7-11.module+el8.6.0+14082+b6f23e95
Rocky Linux:8cjosebefore 0:0.6.1-2.module+el8.3.0+129+2feafa460:0.6.1-2.module+el8.3.0+129+2feafa46
Rocky Linux:8mod_auth_openidcbefore 0:2.3.7-11.module+el8.6.0+840+73eca44e0:2.3.7-11.module+el8.6.0+840+73eca44e
SUSE:Linux Enterprise Module for Server Applications 15 SP4apache2-mod_auth_openidcbefore 2.3.8-150100.3.22.12.3.8-150100.3.22.1
SUSE:Linux Enterprise Module for Server Applications 15 SP6apache2-mod_auth_openidcbefore 2.4.17.1-150600.16.14.12.4.17.1-150600.16.14.1
SUSE:Linux Enterprise Server 12 SP5apache2-mod_auth_openidcbefore 2.4.0-3.23.12.4.0-3.23.1

Same product

openidc: all records

Other highest-scoring records for the same primary product.

  • CVE-2017-6413The "OpenID Connect Relying Party and OAuth 2.0 Resource Server" (aka mod_auth_openidc) module before 2.1.6 for the Apache HTTP Server does
    35Monitor
  • CVE-2017-6062The "OpenID Connect Relying Party and OAuth 2.0 Resource Server" (aka mod_auth_openidc) module before 2.1.5 for the Apache HTTP Server does
    35Monitor
  • CVE-2017-6059Mod_auth_openidc.c in the Ping Identity OpenID Connect authentication module for Apache (aka mod_auth_openidc) before 2.14 allows remote att
    32Monitor

Published before and after this one in the same product

  • ← EarlierCVE-2021-32791Jul 26, 2021 · Hardcoded static IV and AAD with a reused key in AES GCM encryption in mod_auth_openidc
    23Monitor
  • ← EarlierCVE-2021-32792Jul 26, 2021 · XSS vulnerability when using OIDCPreservePost On in mod_auth_openidc
    24Monitor
  • Later →CVE-2022-23527Dec 14, 2022 · Open Redirect in oidc_validate_redirect_url()
    24Monitor

Remediation

Which version to upgrade to

Fix versions compiled from the vendor, package registries and Microsoft. Verify the vendor's note before upgrading.

Product / packageFixed versionSource
almalinux:cjose0.6.1-2.module_el8.6.0+2868+44838709 · AlmaLinux:8Package registry (OSV)
almalinux:cjose-devel0.6.1-2.module_el8.6.0+2868+44838709 · AlmaLinux:8Package registry (OSV)
almalinux:mod_auth_openidc2.3.7-11.module_el8.6.0+2868+44838709 · AlmaLinux:8Package registry (OSV)
debian:libapache2-mod-auth-openidc2.4.9.4-1 · Debian:12Package registry (OSV)
opensuse:apache2-mod_auth_openidc2.3.8-150100.3.22.1 · openSUSE:Leap 15.4Package registry (OSV)
red hat:cjose0:0.6.1-2.module+el8+2454+f890a43a · Red Hat:enterprise_linux:8::appstreamPackage registry (OSV)
red hat:cjose-debuginfo0:0.6.1-2.module+el8+2454+f890a43a · Red Hat:enterprise_linux:8::appstreamPackage registry (OSV)
red hat:cjose-debugsource0:0.6.1-2.module+el8+2454+f890a43a · Red Hat:enterprise_linux:8::appstreamPackage registry (OSV)
red hat:cjose-devel0:0.6.1-2.module+el8+2454+f890a43a · Red Hat:enterprise_linux:8::appstreamPackage registry (OSV)
red hat:mod_auth_openidc0:2.3.7-11.module+el8.6.0+14082+b6f23e95 · Red Hat:enterprise_linux:8::appstreamPackage registry (OSV)
red hat:mod_auth_openidc-debuginfo0:2.3.7-11.module+el8.6.0+14082+b6f23e95 · Red Hat:enterprise_linux:8::appstreamPackage registry (OSV)
red hat:mod_auth_openidc-debugsource0:2.3.7-11.module+el8.6.0+14082+b6f23e95 · Red Hat:enterprise_linux:8::appstreamPackage registry (OSV)
rocky linux:cjose0:0.6.1-2.module+el8.3.0+129+2feafa46 · Rocky Linux:8Package registry (OSV)
rocky linux:mod_auth_openidc0:2.3.7-11.module+el8.6.0+840+73eca44e · Rocky Linux:8Package registry (OSV)
suse:apache2-mod_auth_openidc2.3.8-150100.3.22.1 · SUSE:Linux Enterprise Module for Server Applications 15 SP4Package registry (OSV)
suse:apache2-mod_auth_openidc2.4.0-3.23.1 · SUSE:Linux Enterprise Server 12 SP5Package registry (OSV)

Exploit status

No known public exploit

No public exploit has been observed yet. That doesn't mean you're safe, only that the bar is a little higher.

Research context

For pentesters and researchers: attack profile, score disagreement, timeline, patch commits, credits, variant and chain candidates, bug bounty scope. All derived from existing data; no exploit code.

Timeline

From publication to today: proof of concept, Metasploit module, CISA KEV and fix record. Dates are as reported by the sources.

No dated events beyond publication.

No history yet (it accumulates with the daily EPSS job).

Patch and commit links

Commit, PR and diff links among the references. A starting point for patch-diffing and variant hunting; fixes, not exploits.

Credits

All researchers

Finders, reporters and analysts named in the CNA record. Click a name for that researcher’s other records.

No credits in the CNA record.

Variant candidates

Same product, same weakness class, within 18 months. If the patch missed the root cause, the sibling bug is here.

No nightly-computed relations.

Chain candidates

An authentication bypass and a privilege-requiring bug in the same product, published close together: combined they may become an unauthenticated path.

—

Bug bounty scope

No known public program.

Source: bounty-targets-data (public HackerOne, Bugcrowd, Intigriti, YesWeHack listings).

Technical details

Attack conditions

  • Anyone who can reach it over the internet can trigger it.
  • No account or password is required.
  • A user must open a link or visit a page.
  • No special conditions are required; it is repeatable.

If successful

Confidentiality
low · data can be read
Integrity
low · data or configuration can be modified
Availability
none

Impact can extend beyond the vulnerable component (scope changes).

Attack vector
Network
Attack complexity
Low
Privileges required
None
User interaction
Required
Scope
Changed
Confidentiality impact
Low
Integrity impact
Low
Availability impact
None

Weakness class (CWE)

CWE-601 · URL Redirection to Untrusted Site ('Open Redirect')

CVSS vector

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

nvd-primary

Attack context

MITRE CAPEC attack patterns and ATT&CK techniques for this weakness class (CWE). A starting point for detection rules and threat hunting.

ATT&CK techniques

—

Change log

  1. Fix✗ → ✓

For records you follow, these changes also arrive as notifications. →

References

Show all references (5 more)

Vendor advisories and official records. Exploit/PoC links are deliberately left out.

All records