dbcve.org
Ios XeOperating system · Cisco

CVE-2019-12646

HIGH · 7.5 CVSS v3.1 Published 2019-09-25
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 Network Address Translation (NAT) Session Initiation Protocol (SIP) Application Layer Gateway (ALG) of Cisco IOS XE Software could allow an unauthenticated, remote attacker to cause an affected device to reload. The vulnerability is due to improper processing of transient SIP packets on which NAT is performed on an affected device. An attacker could exploit this vulnerability by using UDP port 5060 to send crafted SIP packets through an affected device that is performing NAT for SIP packets. A successful exploit could allow an attacker to cause the device to reload, resulting in a denial of service (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 Cisco IOS XE's NAT Session Initiation Protocol (SIP) Application Layer Gateway (ALG) allows unauthenticated remote attackers to cause device reload by sending specially crafted SIP packets through UDP port 5060 on devices performing NAT for SIP traffic. The flaw is due to improper processing of transient SIP packets on which NAT is performed.

MitigationApply the Cisco vendor patch for this vulnerability when available. As an interim measure, consider filtering or blocking SIP traffic (UDP port 5060) at the perimeter if SIP NAT traversal is not required in the environment.

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
Ios XeOperating system
Affected:= 15.4\(3\)s= 15.5\(3\)s= 15.6\(1\)s= 16.3.1= 16.4.1= 16.5.1= 16.6.1= 16.7.1= 16.8.1= 16.9.1= 16.10.1= 16.11.1

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. Identify the Cisco IOS XE version
    Run 'show version' on the device and locate the version string (for example, 16.9.1). Compare this against the affected versions: 15.4(3)s, 15.5(3)s, 15.6(1)s, 16.3.1, 16.4.1, 16.5.1, 16.6.1, 16.7.1, 16.8.1, 16.9.1, 16.10.1, 16.11.1
    Affected if The device runs any of the listed IOS XE versions
  2. Verify NAT is configured on the device
    Run 'show running-config | include ip nat' or 'show ip nat statistics' to see if NAT is active
    Affected if NAT is configured and active on the device
  3. Confirm SIP ALG is enabled for NAT
    Run 'show policy-map type inspect session' or examine the running configuration for 'sip-alg' or 'alg sip' under the NAT configuration. Also check with 'show ip alg' if available on the platform
    Affected if SIP ALG (Application Layer Gateway for SIP) is enabled within the NAT configuration
  4. Check if UDP port 5060 is reachable
    Run 'show udp sockets' or 'show connections' and verify if UDP port 5060 (SIP) is listening or has active sessions. Also check access lists for permit statements on UDP 5060
    Affected if UDP port 5060 is open, exposed, or permitted through the device for SIP traffic

The device is affected if it runs any of the listed IOS XE versions, has NAT configured, has SIP ALG enabled within NAT, and UDP port 5060 is accessible for SIP traffic traversal.

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 vendor patch for this vulnerability when available. As an interim measure, consider filtering or blocking SIP traffic (UDP port 5060) at the perimeter if SIP NAT traversal is not required in the environment.

Fix this in Ios Xe Scoped from the published advisory
  • Consultation4.0 h
  • Implementation8.0 h
  • Testing6.0 h
  • Review / QA2.0 h
20.0 hours of engineering $3,500
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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-2019-12646 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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  • No spam, self-promotion, credentials, or personal data