CVE-2024-20312

What it is

A vulnerability in the Intermediate System-to-Intermediate System (IS-IS) protocol of Cisco IOS Software and Cisco IOS XE Software could allow an unauthenticated, adjacent attacker to cause a denial of service (DoS) condition on an affected device. This vulnerability is due to insufficient input validation when parsing an ingress IS-IS packet. An attacker could exploit this vulnerability by sending a crafted IS-IS packet to an affected device after forming an adjacency. A successful exploit could allow the attacker to cause the affected device to reload, resulting in a denial of service (DoS) condition. Note: The IS-IS protocol is a routing protocol. To exploit this vulnerability, an attacker must be Layer 2-adjacent to the affected device and have formed an adjacency.

At a glance

Exploitability

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

Exploit odds

0.3% chance of exploitation in the next 30 days (EPSS).

Fix

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

Timeline

1. 2024-03-27 17:15 UTC PublishedDisclosed publicly on CVE.org and NVD
2. 2026-06-17 07:06 UTC Last updatedMost recent change to the record

Why it ranks here

• Exploited in the wild: no, CISA does not list it.
• Exploit odds: 0.3% in the next 30 days (EPSS).
• Severity: 7.4 HIGH (CVSS).
• Fix: a patch or advisory is linked.

Details

Published

2024-03-27 17:15 UTC

Last modified

2026-06-17 07:06 UTC

Exploit probability

0.3% · EPSS, next 30 days

Weakness

CWE-476 · NULL pointer dereference

Record status

Modified

Affected

• Cisco iOS 15.0\(1\)ex
• Cisco iOS 15.1\(1\)sy
• Cisco iOS 15.1\(1\)sy1
• Cisco iOS 15.1\(1\)sy2
• Cisco iOS 15.1\(1\)sy3
• Cisco iOS 15.1\(1\)sy4
• Cisco iOS 15.1\(1\)sy5
• Cisco iOS 15.1\(1\)sy6

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?

Hand this to your coding agent. It searches your project for the affected products and checks versions. Nothing leaves your machine.

Read https://cve-list.com/agent/cve/CVE-2024-20312.md and follow it. Check whether this project is affected by CVE-2024-20312. Read only. Don't change anything and don't upload my code. Tell me yes, no or not sure, with the file as proof.

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