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Web Security ApplianceApplication · Cisco

CVE-2019-1817

HIGH · 7.5 CVSS v3.1 Published 2019-05-03
Mitigation only
No fix yet — a mitigation exists. There is no fixed release. A documented workaround reduces exposure in the meantime.
See remediation →
84/100
Remediation priority · High
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 the web proxy functionality of Cisco AsyncOS Software for Cisco Web Security Appliance could allow an unauthenticated, remote attacker to cause a denial of service (DoS) condition on an affected device. The vulnerability is due to improper validation of HTTP and HTTPS requests. An attacker could exploit this vulnerability by sending a malformed HTTP or HTTPS request to an affected device. An exploit could allow the attacker to cause a restart of the web proxy process, resulting in a temporary DoS condition.

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 confidence

A vulnerability in the web proxy component of Cisco AsyncOS Software for Cisco Web Security Appliance allows an unauthenticated remote attacker to send malformed HTTP or HTTPS requests that trigger an improper validation failure, causing the web proxy service to restart and create a denial of service condition.

MitigationApply the relevant Cisco security update/patch for AsyncOS Software to remediate this vulnerability. If immediate patching is not possible, consider rate limiting or filtering malicious requests at the network perimeter to reduce exposure.

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
Web Security ApplianceApplication
Affected:= 11.5.1-fcs-115= 11.5.1-fcs-124= 11.5.1-fcs-125= 11.7.0-fcs-334

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
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 checks

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

  1. Confirm Cisco Web Security Appliance hardware or virtual model
    Access the WSA web interface or CLI and verify the device model is a Cisco Web Security Appliance (WSA). In CLI, run 'systemsetup' or check the home page of the web interface.
    Affected if The device is NOT a Cisco Web Security Appliance - this CVE only affects WSA.
  2. Check AsyncOS version
    In the WSA web interface, go to System Administration > AsyncOS Upgrade or run 'version' in the CLI. Note the full AsyncOS version string displayed.
    Affected if The installed version exactly matches 11.5.1-fcs-115, 11.5.1-fcs-124, 11.5.1-fcs-125, or 11.7.0-fcs-334. Versions outside this specific list or with different build numbers are not affected by this CVE.
  3. Verify web proxy service is enabled
    In the WSA web interface, navigate to Security Services > Web Proxy and confirm the service status shows as 'Enabled'. In CLI, run 'proxy' or 'proxyconfig'.
    Affected if The web proxy service is enabled. If the web proxy is disabled, the vulnerability cannot be exploited since it resides in the web proxy component.
  4. Review system logs for proxy restarts
    In the WSA web interface, go to System Administration > Log Subscriptions or use CLI command 'grep -i "proxy" /var/log/ma.log' to search for proxy-related events. Look for sudden web proxy restarts or crashes.
    Affected if Unexpected or unexplained web proxy service restarts are observed, especially occurring without manual intervention or configuration changes.

A user is affected only if they have a Cisco Web Security Appliance running exactly version 11.5.1-fcs-115, 11.5.1-fcs-124, 11.5.1-fcs-125, or 11.7.0-fcs-334 with the web proxy service enabled.

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 relevant Cisco security update/patch for AsyncOS Software to remediate this vulnerability. If immediate patching is not possible, consider rate limiting or filtering malicious requests at the network perimeter to reduce exposure.

Fix this in Web Security Appliance Scoped from the published advisory
  • Consultation3.0 h
  • Implementation3.0 h
  • Testing6.0 h
  • Review / QA2.0 h
14.0 hours of engineering $2,400
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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-2019-1817 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
  • No weaponised exploit code, or anything meant to cause harm
  • No spam, self-promotion, credentials, or personal data