FedoraOperating system · Fedoraproject
CVE-2021-20718
Official description Straight from the sourceThe vendor's or NVD's own wording, published unedited. Authoritative, but often terse — it says what broke, rarely what to do.
NVD · uneditedmod_auth_openidc 2.4.0 to 2.4.7 allows a remote attacker to cause a denial-of-service (DoS) condition via unspecified vectors.
Technical summary Written by usOur analysis, written from the advisory, the CVSS vector and the affected-version data. It adds context the advisory leaves out, and never invents facts that are not in the source.
dbcve analysis · moderate confidencemod_auth_openidc versions 2.4.0 through 2.4.7 contain a denial-of-service vulnerability that can be triggered remotely. The vulnerability allows an attacker to cause the Apache module to become unresponsive or crash, likely through malformed requests or resource exhaustion in the OpenID Connect authentication handling path.
Verify against the referenced sources before acting — the references below are authoritative for this CVE, this summary is not.
Affected products & versions What the vendor confirmedThe version ranges the vendor confirmed as vulnerable. If your version sits inside a range here, treat yourself as exposed until you have upgraded.
NVD · CPE data
FedoraOperating system
= 33= 34>= 2.4.0, <= 2.4.7< 21.3CVSS breakdown How the score is builtThe industry scoring standard. It rates how the flaw is reached, what it takes to exploit, and what an attacker gains — the score is derived from those, not the other way round.
From the vector- Attack vector
- Network
- Complexity
- Low
- Privileges
- None
- User interaction
- None
- Scope
- Unchanged
- Confidentiality
- None
- Integrity
- None
- Availability
- High
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
Am I affected? How to checkSteps we derive from the advisory and the affected-version data, so you can decide whether this CVE reaches your setup. They are a guide, not a scan — your own configuration is the authority.
dbcve checksWork through these to decide whether this CVE applies to you.
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Identify if mod_auth_openidc is installedCheck for the module file: locate libmod_auth_openidc.so or check Apache modules directory (typically /etc/httpd/modules/ on RHEL/Fedora or /usr/lib/apache2/modules/ on Debian). Also run: apachectl -M 2>/dev/null | grep openidcAffected if The mod_auth_openidc module is loaded in Apache
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Determine installed mod_auth_openidc versionRun: rpm -qa | grep mod_auth_openidc (Fedora/RHEL) or dpkg -l | grep mod_auth_openidc (Debian). Alternatively check the module binary directly: /usr/lib/apache2/modules/mod_auth_openidc.so -i or review the package changelog for version 2.4.xAffected if Installed version is 2.4.0 through 2.4.7 inclusive
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Check if OpenID Connect authentication is actively configuredReview Apache configuration files (httpd.conf, ssl.conf, or included vhost configs) for lines containing 'OIDCRedirectURI', 'OIDCClientID', 'OIDCProviderMetadataURL', or 'AuthType openidc'. These directives indicate OIDC auth is enabled.Affected if OIDC authentication directives are present and the module is loaded
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Verify Oracle Essbase installation and versionIf the target is Oracle Essbase, check installation path and version: $ORACLE_HOME/bin/essbase --version or look for version file in the installation directory. Also check if mod_auth_openidc is bundled: find $ORACLE_HOME -name '*openidc*' 2>/dev/nullAffected if Oracle Essbase version is less than 21.3 and uses the vulnerable mod_auth_openidc component
A user is affected if mod_auth_openidc version 2.4.0-2.4.7 is installed AND the OpenID Connect authentication module is loaded and configured in Apache, or Oracle Essbase versions below 21.3 are in use.
Generated from the published advisory. Verify against your own configuration.
Remediation Closing itWhat it takes to close this. Where a vendor fix exists we point at it; where none exists we say so plainly, and can build one. Effort estimates are scoped from the advisory, not from your codebase.
From vendor data21.3
Upgrade mod_auth_openidc to version 2.4.8 or later. If immediate patching is not possible, implement rate limiting on the authentication endpoints and consider restricting access to the OIDC endpoints via network-level controls.
Fix this in Fedora
Scoped from the published advisory
- Consultation2.0 h
- Implementation3.0 h
- Testing4.0 h
- Review / QA1.0 h
An estimate, not a bill — we confirm scope with you before any work starts. Need it this week? Rush from $2,752.
Scan for this in your stack
Free · runs locallyCheck whether your project pulls in CVE-2021-20718 — or any other known-vulnerable package — straight from your lock files. Free and open source; it runs locally and uploads nothing.
References Go to the primary sourcePrimary sources — vendor advisories, patches and trackers. Where our summary and a reference disagree, the reference wins.
Primary sourcesPractitioner notes
ContributedPeer-ranked notes from engineers who’ve handled CVE-2021-20718 in production — separate from our analysis above.
The advisory tells you what broke. It rarely tells you what actually worked. If you’ve dealt with this one, that detail is what the next engineer is searching for.
- The version that genuinely resolved it — not the one the vendor claimed
- A config change or rule that shut the vector down
- A gotcha in the upgrade path that cost you an afternoon
No notes yet
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- Version or environment caveats, and links to real fixes
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