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Ios XeOperating system · Cisco

CVE-2016-6441

CRITICAL · 9.8 CVSS v3.0 Published 2016-11-03
Mitigation only
No fix yet — a mitigation exists. There is no fixed release. A documented workaround reduces exposure in the meantime.
See remediation →
100/100
Remediation priority · Urgent
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 Transaction Language 1 (TL1) code of Cisco ASR 900 Series routers could allow an unauthenticated, remote attacker to cause a reload of, or remotely execute code on, the affected system. This vulnerability affects Cisco ASR 900 Series Aggregation Services Routers (ASR902, ASR903, and ASR907) that are running the following releases of Cisco IOS XE Software: 3.17.0S 3.17.1S 3.17.2S 3.18.0S 3.18.1S. More Information: CSCuy15175. Known Affected Releases: 15.6(1)S 15.6(2)S. Known Fixed Releases: 15.6(1)S2.12 15.6(1.17)S0.41 15.6(1.17)SP 15.6(2)SP 16.4(0.183) 16.5(0.10).

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 buffer overflow or similar memory corruption vulnerability in the Transaction Language 1 (TL1) interface of Cisco ASR 900 Series routers (ASR902, ASR903, ASR907) allows unauthenticated remote attackers to execute arbitrary code or cause device reload. The flaw exists in IOS XE releases 3.17.x-3.18.x and 15.6(1)S/15.6(2)S.

MitigationUpgrade Cisco IOS XE to a fixed release (15.6(1)S2.12, 15.6(1.17)S0.41, 15.6(2)SP, 16.4+, or 16.5+). If immediate patching is not possible, disable or restrict TL1 management access to trusted management networks.

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:= 3.17.0s= 3.17.1s= 3.17.2s= 3.17s= 3.18.0s= 3.18.1s= 3.18s

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
High
Integrity
High
Availability
High

CVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/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 device model
    Run 'show version' or 'show inventory' to confirm the hardware is a Cisco ASR 900 Series router (ASR902, ASR903, or ASR907)
    Affected if The device is not one of these three models, then it is not affected by this specific CVE
  2. Check the installed IOS XE version
    Run 'show version' and locate the IOS XE software version string (typically in the format 3.17.xs or 15.6(x)S)
    Affected if The version matches 3.17.0s, 3.17.1s, 3.17.2s, 3.17s, 3.18.0s, 3.18.1s, 3.18s, or falls within the 3.17.x-3.18.x or 15.6(1)S/15.6(2)S ranges
  3. Verify if TL1 interface is configured
    Run 'show running-config | include tl1' or 'show tl1 status' to check if the Transaction Language 1 interface is enabled on the device
    Affected if TL1 is actively enabled and listening, the device is vulnerable to exploitation
  4. Check TL1 management access controls
    Examine the configuration for TL1 management interface bindings using 'show running-config | section tl1' and verify access lists or management vlan restrictions
    Affected if TL1 is exposed to untrusted networks or has no access restrictions, the device is vulnerable to remote unauthenticated attack

The device is affected if it is an ASR902/ASR903/ASR907 running IOS XE versions 3.17.x-3.18.x or 15.6(1)S/15.6(2)S with the TL1 interface enabled and accessible.

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.

dbcve · scoped
Mitigation available No clean upgrade yet — mitigate in the meantime
Mitigation

Upgrade Cisco IOS XE to a fixed release (15.6(1)S2.12, 15.6(1.17)S0.41, 15.6(2)SP, 16.4+, or 16.5+). If immediate patching is not possible, disable or restrict TL1 management access to trusted management networks.

Recommended fix High confidence

Upgrade to one of the fixed releases: 15.6(1)S2.12, 15.6(1.17)S0.41, 15.6(1.17)SP, 15.6(2)SP, 16.4(0.183), or 16.5(0.10) depending on the current software train

  1. 1. Identify the current Cisco IOS XE version running on the affected ASR902, ASR903, or ASR907 router using 'show version' command
  2. 2. If running 3.17.0S, 3.17.1S, 3.17.2S, 3.18.0S, or 3.18.1S, determine the appropriate fixed release based on the train (15.6.x or 16.x)
  3. 3. Download the fixed Cisco IOS XE software from Cisco.com (requires valid service contract)
  4. 4. Transfer the new IOS XE image to the router using FTP, SCP, or USB storage
  5. 5. Verify the image integrity using 'verify /md5 <file>' command
  6. 6. Configure the new boot variable: 'boot system flash:<new-image-name>'
  7. 7. Save configuration: 'write memory'
  8. 8. Reload the router: 'reload'
Caveat Review Cisco IOS XE release notes for the target version to check for any configuration changes or feature modifications that may affect existing setups

Generated from the published advisory — verify against the referenced sources before acting.

Fix this in Ios Xe Scoped from the published advisory
  • Consultation6.0 h
  • Implementation4.0 h
  • Testing4.0 h
  • Review / QA2.0 h
16.0 hours of engineering $2,880
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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-2016-6441 in production — separate from our analysis above.

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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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