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iOSOperating system · Cisco

CVE-2016-1384

HIGH · 7.5 CVSS v3.0 Published 2016-04-20
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
The NTP implementation in Cisco IOS 15.1 and 15.5 and IOS XE 3.2 through 3.17 allows remote attackers to modify the system time via crafted packets, aka Bug ID CSCux46898.

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

The NTP implementation in Cisco IOS 15.1/15.5 and IOS XE 3.2-3.17 contains a vulnerability allowing remote, unauthenticated attackers to send crafted NTP packets that modify the system time. This is critical because time manipulation can break cryptographic protocols, authentication mechanisms (Kerberos, SSL/TLS), and logging integrity.

MitigationApply the relevant Cisco security updates to upgrade to a fixed IOS/IOS XE version. As an interim control, restrict NTP access using access-lists to permit only trusted management network sources.

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:= 15.1\(1\)s= 15.1\(1\)s1= 15.1\(1\)s2= 15.1\(2\)s= 15.1\(2\)s1= 15.1\(2\)s2= 15.1\(3\)s= 15.1\(3\)s0a= 15.1\(3\)s1= 15.1\(3\)s2= 15.1\(3\)s3= 15.1\(3\)s4
Ios XeOperating system
Affected:= 3.2.0ja= 3.2.0s= 3.2.0se= 3.2.0sg= 3.2.0xo= 3.2.1s= 3.2.1se= 3.2.1sg= 3.2.1xo= 3.2.2s= 3.2.2se= 3.2.2sg

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. Identify the device OS and version
    Run 'show version' on the Cisco device CLI and note the IOS or IOS XE version string (e.g., 15.1(1)s, 15.1(3)S4, 3.2.0JA)
    Affected if The version matches any of the specific affected versions listed in the CVE: iOS 15.1(1)s through 15.1(3)S4, or IOS XE 3.2.0JA through 3.2.2SG
  2. Verify NTP is enabled on the device
    Run 'show running-config | include ntp' or 'show ntp status' to check if NTP is configured
    Affected if NTP is enabled and the device is using a vulnerable version
  3. Check NTP mode and configuration
    Run 'show ntp associations detail' to see configured NTP servers and the mode (client/server)
    Affected if The device is configured as an NTP client accepting requests from any source
  4. Review NTP access control settings
    Run 'show running-config | include access-list' and inspect any access-lists applied to NTP, or check NTP-specific access restrictions with 'show ntp associations'
    Affected if No access-list restricts NTP to trusted sources, meaning NTP is accessible from any network

The device is affected if it runs a matching vulnerable iOS/IOS XE version AND has NTP enabled with unrestricted network access.

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 updates to upgrade to a fixed IOS/IOS XE version. As an interim control, restrict NTP access using access-lists to permit only trusted management network sources.

Fix this in iOS Scoped from the published advisory
  • Consultation6.0 h
  • Implementation4.0 h
  • Testing3.0 h
  • Review / QA2.0 h
15.0 hours of engineering $2,730
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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-2016-1384 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