CVE-2018-20745
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 · uneditedYii 2.x through 2.0.15.1 actively converts a wildcard CORS policy into reflecting an arbitrary Origin header value, which is incompatible with the CORS security design, and could lead to CORS misconfiguration security problems.
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 · high confidenceYii 2.x through 2.0.15.1 contains a CORS misconfiguration where the framework actively converts a wildcard CORS policy into reflecting arbitrary Origin header values. This defeats the purpose of CORS security by allowing any website to make cross-origin requests, potentially enabling cross-site scripting (XSS) or data theft attacks through malicious cross-origin requests.
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>= 2.0, <= 2.0.15.1CVSS 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
- High
- Privileges
- None
- User interaction
- None
- Scope
- Unchanged
- Confidentiality
- None
- Integrity
- High
- Availability
- None
CVSS:3.0/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:H/A:N
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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Determine installed Yii versionLocate the Yii version file or entry point (commonly in vendor/yiisoft/yii2/BaseYii.php or through composer show yiisoft/yii2), or check the framework version via your application's configurationAffected if The installed Yii version is 2.0.x where x is 0 through 15.1 (inclusive)
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Verify CORS component is in useCheck your application configuration files (main.php, params.php, or web.php in config/ directory) for the yii\filters\Cors component listed in the behaviors() of controllers or application componentsAffected if CORS filtering is configured and active in your application
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Inspect CORS allowedOrigins configurationExamine the CORS configuration where allowedOrigins is defined - typically in controller behaviors() or a CORS filter configuration file. Look for the value of 'allowedOrigins' settingAffected if The allowedOrigins is set to ['*'] (asterisk/wildcard) or contains logic that dynamically reflects the Origin header (for example, using $_SERVER['HTTP_ORIGIN'] or similar dynamic assignment)
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Check for dynamic origin reflection patternReview CORS filter code or configuration for patterns where allowedOrigins uses array_merge, preg_match, or other logic that could reflect incoming Origin headers back as allowed originsAffected if The configuration dynamically reflects the request Origin header into the allowed origins without validation
You are affected if your Yii version is between 2.0 and 2.0.15.1 AND you have CORS enabled with a wildcard or Origin-reflection configuration in allowedOrigins.
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 dataConfigure CORS with explicit allowed origins rather than wildcards or dynamic origin reflection. Review and restrict the allowed origins to only legitimate domains that require cross-origin access, and upgrade to Yii 2.0.15.1 or later if a patch is available.
- Consultation2.0 h
- Implementation2.0 h
- Testing1.0 h
- Review / QA1.0 h
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Scan for this in your stack
Free · runs locallyCheck whether your project pulls in CVE-2018-20745 — 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-2018-20745 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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- Verified mitigations, workarounds, and config changes
- Version or environment caveats, and links to real fixes
- No weaponised exploit code, or anything meant to cause harm
- No spam, self-promotion, credentials, or personal data