Ios XrOperating system · Cisco

CVE-2019-1910

HIGH · 7.4 CVSS v3.1 Published 2019-08-07

Fix available

A fix is available. Upgrade to 6.6.3 or later.

See remediation →

79/100

Remediation priority · High

No privileges Zero-click

Official description

NVD · unedited

A vulnerability in the implementation of the Intermediate System–to–Intermediate System (IS–IS) routing protocol functionality in Cisco IOS XR Software could allow an unauthenticated attacker who is in the same IS–IS area to cause a denial of service (DoS) condition. The vulnerability is due to incorrect processing of crafted IS–IS link-state protocol data units (PDUs). An attacker could exploit this vulnerability by sending a crafted link-state PDU to an affected system to be processed. A successful exploit could allow the attacker to cause all routers within the IS–IS area to unexpectedly restart the IS–IS process, resulting in a DoS condition. This vulnerability affects Cisco devices if they are running a vulnerable release of Cisco IOS XR Software earlier than Release 6.6.3 and are configured with the IS–IS routing protocol. Cisco has confirmed that this vulnerability affects both Cisco IOS XR 32-bit Software and Cisco IOS XR 64-bit Software.

Technical summary

dbcve analysis · high confidence

A vulnerability in the IS-IS routing protocol implementation in Cisco IOS XR Software allows an unauthenticated attacker in the same IS-IS area to send a crafted link-state PDU that causes all routers in the area to unexpectedly restart the IS-IS process, resulting in denial of service.

MitigationUpgrade to Cisco IOS XR Software Release 6.6.3 or later, or implement IS-IS MD5 authentication to prevent processing of unauthenticated PDUs.

Verify against the referenced sources before acting — the references below are authoritative for this CVE, this summary is not.

Affected products & versions

NVD · CPE data

Ios XrOperating system

Affected:< 6.6.3

Carrier Routing SystemApplication

Affected:= 7.0.1

CVSS breakdown

From the vector

Attack vector: Adjacent
Complexity: Low
Privileges: None
User interaction: None
Scope: Changed
Confidentiality: None
Integrity: None
Availability: High

CVSS:3.1/AV:A/AC:L/PR:N/UI:N/S:C/C:N/I:N/A:H

Am I affected?

dbcve checks

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

Identify device and software version

Execute 'show version' or access the device management interface to determine if the device runs Cisco IOS XR software or Cisco Carrier Routing System, and record the exact software version number.

Affected if The device runs Cisco IOS XR with version lower than 6.6.3, or runs Cisco Carrier Routing System version 7.0.1.
Verify IS-IS protocol is enabled

Execute 'show isis protocol' or 'show isis adjacency' to check if the IS-IS routing protocol is configured and active on the device.

Affected if IS-IS protocol is enabled and the device is participating in an IS-IS area.
Check IS-IS process status

Execute 'show isis process' or check process monitoring to determine if the IS-IS routing process is running.

Affected if The IS-IS process is running and handling link-state PDUs.
Verify IS-IS authentication configuration

Execute 'show isis configuration' or review the IS-IS configuration to determine if MD5 authentication is configured for the IS-IS area or interface.

Affected if MD5 authentication is NOT configured for IS-IS, meaning the device will process unauthenticated link-state PDUs.

A device is affected if it runs Cisco IOS XR version below 6.6.1 or exactly 7.0.1 on CRS, has IS-IS enabled, and does not have IS-IS MD5 authentication configured.

Generated from the published advisory. Verify against your own configuration.

Remediation

From vendor data

Upgrade available Upgrade to 6.6.3 or later

Fixed in 6.6.3

Interim mitigation

Upgrade to Cisco IOS XR Software Release 6.6.3 or later, or implement IS-IS MD5 authentication to prevent processing of unauthenticated PDUs.

Fix this in Ios Xr Scoped from the published advisory

Consultation4.0 h
Implementation8.0 h
Testing4.0 h
Review / QA2.0 h

18.0 hours of engineering $3,200

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Scan for this in your stack

Free · runs locally

dbcve dependency scanner

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References

Primary sources

tools.cisco.comVendor Advisory
nvd.nist.govNVD record

Practitioner notes

Contributed

Peer-ranked notes from engineers who’ve handled CVE-2019-1910 in production — separate from our analysis above.

Notes0 Guidelines

Know something about CVE-2019-1910?

The advisory tells you what broke. It rarely tells you what actually worked. If you’ve dealt with this one, that detail is what the next engineer is searching for.

The version that genuinely resolved it — not the one the vendor claimed
A config change or rule that shut the vector down
A gotcha in the upgrade path that cost you an afternoon

No notes yet

Be the first to add a field note for this CVE — a mitigation you’ve verified, a version caveat, or a link to a working fix. Sign in above to contribute.

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

At a glance

A fix existsUpgrade to 6.6.3 or later

Severity 7.4 High

Exploit likelihood EPSS, next 30 days 0.4%

Affects: Ios Xr

Remediation

A high-priority fix

Fix this in Ios Xr 18 hrs · Moderate

Typical engagement from $3,200

Get a fix See the full breakdown ↓

A high-priority vulnerability. Send your environment and a specialist will scope CVE-2019-1910 and return a fixed quote and timeline.

You’ll deal with our team directly and deploy the reviewed fix to staging first — never straight to production.

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.

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.

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.

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.

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.

Check your environment

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.

Scan for this in your stack

References Go to the primary sourcePrimary sources — vendor advisories, patches and trackers. Where our summary and a reference disagree, the reference wins.

Practitioner notes

No notes yet

Official description

Technical summary

Affected products & versions

CVSS breakdown

Am I affected?

Remediation

References