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Firepower System SoftwareApplication · Cisco

CVE-2018-15443

HIGH · 7.5 CVSS v3.0 Published 2018-11-08
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 detection engine of Cisco Firepower System Software could allow an unauthenticated, remote attacker to bypass a configured Intrusion Prevention System (IPS) rule that inspects certain types of TCP traffic. The vulnerability is due to incorrect TCP retransmission handling. An attacker could exploit this vulnerability by sending a crafted TCP connection request through an affected device. A successful exploit could allow the attacker to bypass configured IPS rules and allow uninspected traffic onto the network.

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

Cisco Firepower System Software contains a vulnerability in its IPS detection engine where incorrect TCP retransmission handling allows attackers to craft specific TCP connection requests that bypass configured intrusion prevention rules. By sending specially crafted TCP packets with manipulated retransmission sequences, an unauthenticated remote attacker can cause the IPS to fail to inspect certain TCP traffic, permitting uninspected connections onto the protected network.

MitigationApply the Cisco security patch for this vulnerability to the Firepower System Software; until patched, consider implementing additional network-layer controls or compensating detection mechanisms to identify bypassed traffic.

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
Firepower System SoftwareApplication
Affected:all versions

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
High
Availability
None

CVSS:3.0/AV:N/AC:L/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 checks

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

  1. Confirm Cisco Firepower System Software is deployed
    Identify the installed product by checking system inventory, running processes (e.g., 'show version' on the device), or network device identification. Cisco Firepower is typically deployed as a physical appliance, virtual appliance, or integrated with Cisco ASA with FirePOWER module.
    Affected if The system is running Cisco Firepower System Software - all versions are affected by this vulnerability.
  2. Verify IPS (Intrusion Prevention System) is enabled
    Access the Firepower Management Center or run appropriate CLI commands (e.g., 'show intrusion-config' or check the assigned intrusion policy) to determine if an IPS policy is actively applied to any security zone or interface.
    Affected if IPS inspection is enabled and processing traffic - the bypass only affects traffic that should be inspected by the IPS detection engine.
  3. Assess network exposure to untrusted sources
    Review Firepower interface configurations and security zone assignments to identify any interfaces accepting TCP connections from untrusted or external networks (such as internet-facing interfaces or DMZ connections).
    Affected if The Firepower device is processing TCP traffic from untrusted/external sources - the attacker requires the ability to send crafted TCP packets to the protected interface.
  4. Review intrusion events for inspection gaps
    Analyze intrusion event logs in the Firepower Management Center for any anomalies such as missing inspection events on active connections, unusual TCP session patterns, or connections that bypassed IPS inspection. Look for events with unusual TCP flags or retransmission patterns.
    Affected if There are gaps in intrusion inspection logs or connections that passed without expected IPS evaluation, potentially indicating the bypass was exploited.

You are affected if you run Cisco Firepower System Software with IPS enabled on interfaces exposed to untrusted TCP traffic, since all versions of this product contain the vulnerability.

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 Cisco security patch for this vulnerability to the Firepower System Software; until patched, consider implementing additional network-layer controls or compensating detection mechanisms to identify bypassed traffic.

Fix this in Firepower System Software Scoped from the published advisory
  • Consultation4.0 h
  • Implementation6.0 h
  • Testing8.0 h
  • Review / QA4.0 h
22.0 hours of engineering $3,800
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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-2018-15443 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
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  • Version or environment caveats, and links to real fixes
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