dbcve.org
AsyncosOperating system · Cisco

CVE-2025-20183

MEDIUM · 5.3 CVSS v3.1 Published 2025-02-05
Mitigation only
No fix yet — a mitigation exists. There is no fixed release. A documented workaround reduces exposure in the meantime.
See remediation →
62/100
Remediation priority · Elevated
Remotely reachable No privileges Zero-click

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 · unedited
A vulnerability in a policy-based Cisco Application Visibility and Control (AVC) implementation of Cisco AsyncOS Software for Cisco Secure Web Appliance could allow an unauthenticated, remote attacker to evade the antivirus scanner and download a malicious file onto an endpoint.  The vulnerability is due to improper handling of a crafted range request header. An attacker could exploit this vulnerability by sending an HTTP request with a crafted range request header through the affected device. A successful exploit could allow the attacker to evade the antivirus scanner and download malware onto the endpoint without detection by Cisco Secure Web Appliance.

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 confidence

A vulnerability in the policy-based AVC (Application Visibility and Control) implementation of Cisco AsyncOS Software for Cisco Secure Web Appliance allows an unauthenticated remote attacker to bypass antivirus scanning by sending HTTP requests with a crafted range request header. This enables download of malicious files onto endpoints without detection.

MitigationApply the vendor patch from Cisco when available; until then, monitor for suspicious HTTP traffic with range headers and consider additional perimeter controls.

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
AsyncosOperating system
Affected:= 11.8.0-414= 11.8.0-429= 11.8.0-453= 11.8.1-023= 11.8.3-018= 11.8.3-021= 11.8.4-004= 12.0.1-268= 12.0.1-334= 12.0.2-004= 12.0.2-012= 12.0.3-005

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
None
Integrity
Low
Availability
None

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/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 checks

Work through these to decide whether this CVE applies to you.

  1. Identify the AsyncOS version
    Log into the Secure Web Appliance CLI and run the 'version' command, or check the web UI under System Administration > Software Updates > Installed Software
    Affected if The installed version matches any of these: 11.8.0-414, 11.8.0-429, 11.8.0-453, 11.8.1-023, 11.8.3-018, 11.8.3-021, 11.8.4-004, 12.0.1-268, 12.0.1-334, 12.0.2-004, 12.0.2-012, 12.0.3-005
  2. Verify AVC is enabled
    In the web UI, navigate to Security Services > AVC and confirm the policy is turned on. In CLI, use 'avcconfig' to check status
    Affected if AVC is enabled and scanning is active on the device
  3. Review HTTP traffic logs for range header anomalies
    Check the access logs or AVC logs under Security Services > AVC > View Logs for HTTP requests containing Range headers that may have bypassed scanning
    Affected if Logs show HTTP traffic with Range headers that was not scanned or flagged by AVC despite matching policy conditions
  4. Check for antivirus scanning bypass indicators
    Compare the number of HTTP downloads logged in access logs against the number of AV scans logged in AVC or scanning logs
    Affected if A significant discrepancy exists where downloads occurred without corresponding AV scan records

You are affected if your Secure Web Appliance runs an affected AsyncOS version AND has AVC enabled, with evidence of HTTP Range-header requests bypassing antivirus scanning.

Generated from the published advisory. Verify against your own configuration.

Check your environment

Paste your version and any relevant configuration and it will be compared against the affected criteria above. Do not include secrets or credentials.

AI-assisted, checked against the advisory. Informational, not a guarantee.

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 data
Mitigation available No clean upgrade yet — mitigate in the meantime
Mitigation

Apply the vendor patch from Cisco when available; until then, monitor for suspicious HTTP traffic with range headers and consider additional perimeter controls.

Fix this in Asyncos Scoped from the published advisory
  • Consultation3.0 h
  • Implementation4.0 h
  • Testing3.0 h
  • Review / QA2.0 h
12.0 hours of engineering $2,130
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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 sources

Practitioner notes

Contributed

Peer-ranked notes from engineers who’ve handled CVE-2025-20183 in production — separate from our analysis above.

No notes yet

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What this is

A place for practitioners to share what actually worked: a mitigation you’ve tested, a configuration change, a version- or environment-specific caveat, or a link to a verified patch. The most useful notes rise to the top as peers upvote them, so the signal stays high.

What belongs here
  • Verified mitigations, workarounds, and config changes
  • Version or environment caveats, and links to real fixes
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