CVE-2019-1918

What it is

A vulnerability in the implementation of 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 IS–IS link-state protocol data units (PDUs). An attacker could exploit this vulnerability by sending specific link-state PDUs to an affected system to be processed. A successful exploit could allow the attacker to cause incorrect calculations used in the weighted remote shared risk link groups (SRLG) or in the IGP Flexible Algorithm. It could also cause tracebacks to the logs or potentially cause the receiving device to crash the IS–IS process, resulting in a DoS condition.

At a glance

Exploitability

Can be exploited from the same network segment without logging in. High risk of service disruption.

Exploit odds

0.5% chance of exploitation in the next 30 days (EPSS).

Fix

A patch, advisory or fixed version is referenced. Upgrade or apply it.

Timeline

1. 2019-08-07 22:15 UTC PublishedDisclosed publicly on CVE.org and NVD
2. 2026-06-17 02:29 UTC Last updatedMost recent change to the record

Why it ranks here

• Exploited in the wild: no, CISA does not list it.
• Exploit odds: 0.5% in the next 30 days (EPSS).
• Severity: 7.4 HIGH (CVSS).
• Fix: a patch or advisory is linked.

Details

Published

2019-08-07 22:15 UTC

Last modified

2026-06-17 02:29 UTC

Exploit probability

0.5% · EPSS, next 30 days

Weakness

CWE-20 · Improper input validation

Record status

Modified

Affected

• Cisco iOS Xr < 6.6.3
• Cisco Carrier Routing System 6.5.1
• Cisco Carrier Routing System 6.5.3

Attack profile CVSS 3.1 · 7.4

Attack vector

Adjacent network

Complexity

Low

Privileges needed

None

User interaction

None

Scope

Changed

Confidentiality

None

Integrity

None

Availability

High

Is it in your code?

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