dbcve.org
iOSOperating system · Cisco

CVE-2018-15369

MEDIUM · 6.8 CVSS v3.0 Published 2018-10-05
Mitigation only
No fix yet — a mitigation exists. There is no fixed release. A documented workaround reduces exposure in the meantime.
See remediation →
77/100
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 TACACS+ client subsystem of Cisco IOS Software and Cisco IOS XE Software could allow an unauthenticated, remote attacker to cause an affected device to reload, resulting in a denial of service (DoS) condition. The vulnerability is due to improper handling of crafted TACACS+ response packets by the affected software. An attacker could exploit this vulnerability by injecting a crafted TACACS+ packet into an existing TACACS+ session between an affected device and a TACACS+ server or by impersonating a known, valid TACACS+ server and sending a crafted TACACS+ packet to an affected device when establishing a connection to the device. To exploit this vulnerability by using either method, the attacker must know the shared TACACS+ secret and the crafted packet must be sent in response to a TACACS+ request from a TACACS+ client. A successful exploit could allow the attacker to cause the affected device to reload, resulting in a 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 TACACS+ client of Cisco IOS/IOS XE Software allows an attacker with knowledge of the shared TACACS+ secret to cause device reload by sending crafted TACACS+ response packets, either by injecting into an existing session or impersonating a TACACS+ server.

MitigationApply the appropriate Cisco IOS/IOS XE software update from the Cisco security advisory. Ensure the TACACS+ shared secret is properly secured and consider network segmentation to limit exposure to attackers who might obtain the secret.

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
iOSOperating system
Affected:= 15.6\(1.9\)t
Ios XeOperating system
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
High
Privileges
None
User interaction
None
Scope
Changed
Confidentiality
None
Integrity
None
Availability
High

CVSS:3.0/AV:N/AC:H/PR:N/UI:N/S:C/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. Identify the Cisco IOS or IOS XE version
    Run 'show version' and locate the version string (e.g., 15.6(1.9)t) or IOS XE version (e.g., 16.x, 17.x)
    Affected if The device runs iOS version 15.6(1.9)t or any version of IOS XE
  2. Confirm TACACS+ client is configured
    Run 'show running-config | include tacacs' to check for TACACS+ server or key configuration
    Affected if TACACS+ configuration exists (tacacs server or tacacs-server keywords appear in output)
  3. Check for active TACACS+ authentication configuration
    Run 'show running-config | include aaa' and look for 'tacacs' in authentication, authorization, or accounting lines
    Affected if AAA authentication or authorization references TACACS+ (e.g., 'login authentication tacacs', 'tacacs-server')
  4. Verify TACACS+ server entries exist
    Run 'show tacacs' or check 'tacacs server' configuration in running config
    Affected if One or more TACACS+ servers are defined in the device configuration

The device is affected if it runs Cisco iOS 15.6(1.9)t or any Cisco IOS XE version AND has TACACS+ client configuration present (server defined or AAA referencing TACACS).

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 appropriate Cisco IOS/IOS XE software update from the Cisco security advisory. Ensure the TACACS+ shared secret is properly secured and consider network segmentation to limit exposure to attackers who might obtain the secret.

Fix this in iOS Scoped from the published advisory
  • Consultation3.0 h
  • Implementation4.0 h
  • Testing2.0 h
  • Review / QA2.0 h
11.0 hours of engineering $1,980
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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-2018-15369 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