Application Policy Infrastructure ControllerApplication · Cisco
CVE-2021-1577
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 vulnerability in an API endpoint of Cisco Application Policy Infrastructure Controller (APIC) and Cisco Cloud Application Policy Infrastructure Controller (Cloud APIC) could allow an unauthenticated, remote attacker to read or write arbitrary files on an affected system. This vulnerability is due to improper access control. An attacker could exploit this vulnerability by using a specific API endpoint to upload a file to an affected device. A successful exploit could allow the attacker to read or write arbitrary files on an affected device.
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 confidenceThis is an improper access control vulnerability in a specific API endpoint of Cisco Application Policy Infrastructure Controller (APIC) and Cloud APIC that allows an unauthenticated, remote attacker to read or write arbitrary files on the affected system by uploading files through the API.
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
Application Policy Infrastructure ControllerApplication
< 3.2\(10e\)>= 4.0, < 4.2\(6h\)>= 5.0, < 5.1\(3e\)
Cloud Application Policy Infrastructure ControllerApplication
< 3.2\(10e\)>= 4.0, < 4.2\(6h\)>= 5.0, < 5.1\(3e\)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
- Low
- Privileges
- None
- User interaction
- None
- Scope
- Unchanged
- Confidentiality
- High
- Integrity
- High
- Availability
- None
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/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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Identify the installed productDetermine whether the system is running Cisco Application Policy Infrastructure Controller (APIC) or Cisco Cloud Application Policy Infrastructure Controller (Cloud APIC). Check the product name in the system inventory or about page.Affected if The product is Cisco APIC or Cloud APIC.
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Determine the installed software versionRun 'show version' or access the controller GUI under the Administration > System > Controller Nodes section to retrieve the current software version number.Affected if The installed version is less than 3.2(10e), OR between 4.0 and 4.2(6h) inclusive, OR between 5.0 and 5.1(3e) inclusive.
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Verify API access controlsInspect the API endpoint configuration or proxy settings to determine whether unauthenticated API access is permitted. Check for any custom access control rules on the API service (typically port 443/TCP on the APIC cluster).Affected if The API endpoint is accessible without authentication from untrusted networks.
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Confirm file upload API functionalityReview the API documentation or system logs to identify if the specific API endpoint that allows file uploads is enabled and reachable. This is the endpoint used for file operations through the API.Affected if The file upload API endpoint is exposed and operational on the affected system.
A system is affected if it is running Cisco APIC or Cloud APIC with a version in the vulnerable ranges AND the API endpoint is accessible, allowing unauthenticated remote file read/write access.
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.
dbcve · scoped3.24.25.1
Apply the vendor-supplied patch or software update for Cisco APIC/Cloud APIC as soon as possible, as this is a critical unauthenticated remote code vulnerability allowing arbitrary file access.
Application Policy Infrastructure Controller: 3.2(10e), 4.2(6h), or 5.1(3e) and later | Cloud Application Policy Infrastructure Controller: 3.2(10e), 4.2(6h), or 5.1(3e) and later
- 1. Identify the current version of Cisco Application Policy Infrastructure Controller (APIC) or Cloud APIC running in your environment
- 2. Based on your current major version, plan the upgrade path: If on 3.x, upgrade to 3.2(10e) or later; If on 4.x, upgrade to 4.2(6h) or later; If on 5.0.x, upgrade to 5.1(3e) or later
- 3. Review Cisco's upgrade documentation and release notes for the target version to ensure compatibility with your environment
- 4. Create a backup of the current configuration
- 5. Schedule a maintenance window as upgrades may require downtime
- 6. Perform the upgrade following Cisco's documented upgrade procedure
- 7. After upgrade, verify the new version is running and all services are operational
- 8. Validate that the API endpoint vulnerability is no longer present
Generated from the published advisory — verify against the referenced sources before acting.
Fix this in Application Policy Infrastructure Controller
Scoped from the published advisory
- Consultation3.0 h
- Implementation2.0 h
- Testing4.0 h
- Review / QA2.0 h
An estimate, not a bill — we confirm scope with you before any work starts. Need it this week? Rush from $3,072.
Scan for this in your stack
Free · runs locallyCheck whether your project pulls in CVE-2021-1577 — 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-2021-1577 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
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