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CVE Record

CVE-2019-1910: Cisco IOS XR Software Intermediate System to Intermediate System Denial of Service Vulnerability

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.

HighCVSS 7.4Not KEV-listedUpdated
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Glexia's TakeAutomated analysishigh

Security readout for executives and security teams

Plain-English summary

This vulnerability can disrupt routing inside an IS-IS area on affected Cisco IOS XR devices. A nearby attacker in the same routing area could trigger IS-IS process restarts across routers, causing a denial of service without needing credentials.

Executive priority

Prioritize remediation for core, provider, or data-center routers using IS-IS, because exploitation can affect routing availability across an area and disrupt dependent services.

Technical view

Cisco describes incorrect processing of crafted IS-IS link-state PDUs in IOS XR. Affected systems are IOS XR 32-bit and 64-bit releases earlier than 6.6.3 when configured for IS-IS. The CVSS 3.0 score is 7.4, with adjacent attack vector and high availability impact.

Likely exposure

Exposure is likely limited to Cisco IOS XR routers running pre-6.6.3 software with IS-IS enabled, especially where untrusted systems can participate in the same IS-IS area.

Exploitation context

The supplied sources say exploitation requires access to the same IS-IS area and no authentication. The bundle does not show CISA KEV listing or other evidence of active exploitation.

Researcher notes

Key constraints are important: attacker locality is the same IS-IS area, impact is availability only, and the vulnerable condition depends on IOS XR plus IS-IS configuration. The source bundle does not provide packet details or named workarounds beyond fixed releases.

Mitigation direction

  • Identify Cisco IOS XR routers configured for IS-IS.
  • Upgrade affected IOS XR systems to Release 6.6.3 or later per Cisco guidance.
  • Restrict IS-IS participation to trusted routing infrastructure where operationally feasible.
  • Review Cisco's advisory for fixed releases and deployment caveats.

Validation and detection

  • Confirm each IOS XR software version against the Cisco advisory.
  • Verify whether IS-IS is enabled on each IOS XR router.
  • Check routing-domain design for untrusted IS-IS area adjacency risk.
  • Monitor for unexpected IS-IS process restarts or routing instability.
Prepared
Confidence
high
Sources
3

Public sources used

Generated from the cited source records. This long-tail analysis has not been individually reviewed by a named human.

Potential ATT&CK relevance

Conservative CVE-to-ATT&CK context

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CVE-2019-1910 mapping review

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Vulnerability profileCVE Program record
Severity
High
CVSS
7.4 (3.0)
Known Exploited
No
Published

Vector: CVSS:3.0/AV:A/AC:L/PR:N/UI:N/S:C/C:N/I:N/A:H

Official CVE source material

CNA and ADP enrichment extracted from CVE v5

These fields come from the CVE record and ADP containers, not from Glexia's Take. They preserve time-varying source decisions such as CISA SSVC, KEV status, CVSS metrics, and provider references.

1CVSS vectors
0Timeline events
0ADP providers
2Source links

CVSS vector scores

1 official score

We collect every scored CVSS vector available in the official CNA and ADP containers. When more than one version is present, the table keeps the source vectors side by side instead of collapsing them into the highest score.

ScoreVersionSeverityVectorExploitImpactSource
7.4CVSS 3.0HighCVSS:3.0/AV:A/AC:L/PR:N/UI:N/S:C/C:N/I:N/A:H2.84Primary CVE score

Vulnerability scoring details

Base CVSS 3.0 score

7.4High
CVSS 3.0 vector shape for CVE-2019-1910Attack VectorAttack ComplexityPrivileges RequiredUser InteractionScopeConfidentiality ImpactIntegrity ImpactAvailability Impact

Vector: CVSS:3.0/AV:A/AC:L/PR:N/UI:N/S:C/C:N/I:N/A:H

Attack Vector
NetworkAdjacentLocalPhysical
Attack Complexity
LowHigh
Privileges Required
NoneLowHigh
User Interaction
NoneRequired
Scope
ChangedUnchanged
Confidentiality Impact
HighLowNone
Integrity Impact
HighLowNone
Availability Impact
HighLowNone

Source materials

Affected products

Products and packages named in the record

VendorProductVersion / packageStatus
CiscoCisco IOS XR SoftwareunspecifiedListed
Weakness

CWE details

CWE-20

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Improper Input Validation

Improper Input Validation represents a recurring weakness pattern that can create exploitable paths when design, validation, or implementation controls are missing.

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