CVE-2026-9304
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 · uneditedA security flaw has been discovered in calcom cal.diy up to 4.9.4. The affected element is the function validateUrlForSSRF of the file apps/web/app/api/logo/route.ts of the component Logo API. The manipulation results in server-side request forgery. It is possible to launch the attack remotely. Attacks of this nature are highly complex. The exploitability is described as difficult. The exploit has been released to the public and may be used for attacks. The vendor was contacted early about this disclosure but did not respond in any way.
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 confidenceServer-side request forgery (SSRF) vulnerability in calcom cal.diy's Logo API (apps/web/app/api/logo/route.ts). The validateUrlForSSRF function fails to properly validate user-supplied URLs, allowing attackers to make the server perform requests to internal resources or unintended external destinations.
Verify against the referenced sources before acting — the references below are authoritative for this CVE, this summary is not.
CVSS 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
- Low
- User interaction
- None
- Scope
- Unchanged
- Confidentiality
- Low
- Integrity
- Low
- Availability
- Low
CVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:U/C:L/I:L/A:L
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 Cal.com installationLocate the Cal.com installation and determine the deployment type (self-hosted, caldiy instance, etc.)Affected if Cal.com or cal.diy variant is deployed
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Check Cal.com versionRun 'grep -r "version" package.json' or check the installed package version (e.g., @calcom/diy package)Affected if Version is within the vulnerable range and has not been patched
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Verify cal.diy Logo API endpoint existsInspect the file apps/web/app/api/logo/route.ts in the codebase or check if the /api/logo endpoint is accessibleAffected if The endpoint exists and responds to requests
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Confirm validateUrlForSSRF function is presentSearch for the validateUrlForSSRF function in the codebase (apps/web/lib/validateUrlForSSRF.ts or similar) and review its implementationAffected if The function exists but does not block internal IP ranges, localhost, or cloud metadata endpoints (169.254.169.254)
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Test URL validation behaviorSend a request to /api/logo with a crafted URL pointing to internal resources (e.g., 127.0.0.1, 169.254.169.254) and observe if the server makes the requestAffected if The server successfully processes and attempts to fetch URLs pointing to internal or metadata endpoints
If Cal.com with cal.diy is deployed, the vulnerable validateUrlForSSRF function is present, and the /api/logo endpoint accepts URLs to internal resources, the environment is affected by this SSRF vulnerability.
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 dataImplement strict allowlist-based URL validation in validateUrlForSSRF, restrict accessible protocols and hostnames, and add network segmentation to limit impact of potential SSRF attacks.
- Consultation2.0 h
- Implementation3.0 h
- Testing2.0 h
- Review / QA2.0 h
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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-2026-9304 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
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- Version or environment caveats, and links to real fixes
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