Cisco IOS Verification Flaw Let Attackers Execute Arbitrary Code

Cisco has been discovered with an arbitrary code execution flaw on their Cisco IOS XR Software image verification checks, which allows an authenticated, local attacker to execute arbitrary code on their underlying operating system.

Cisco Internetwork Operating System (IOS) is a network operating system that can be used in large-scale enterprise environments for high-performance and reliable routing. It is a privately owned Operating System that runs on the Cisco Systems routers and switches. 

CVE-2023-20135: Cisco IOS XR Image Verification Vulnerability

This is a Time-of-Check Time-of-use (TOCTOU) race condition due to the install query sent to the ISO image during an ISO install operation. A threat actor can exploit this by modifying an ISO image and carrying out the install requests in parallel, resulting in an arbitrary code execution if the exploitation succeeds.

CISCO SYSTEMS GIVES the CVSS score for this vulnerability as 5.7 (Medium). Cisco has released a security advisory for addressing this vulnerability.

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Affected Products

As per the reports shared with Cyber Security News, the affected products are as mentioned below,

• 8000 Series Routers
• Network Convergence System (NCS) 540 Series Routers that are running the NCS540L images
• Network Convergence System (NCS) 5700 Series Routers that are running the NCS5700 images (NCS-57B1-5DSE-SYS, NCS-57B1-6D24-SYS and NCS-57C1-48Q6-SYS)

However, Cisco has confirmed that this product does not affect IOS Software, IOS XE Software, and NX-OS Software.

Fixed in Release

Cisco IOS XR Release	First Fixed Release
Earlier than 7.5.2	Not affected.
7.5.2 and later	Migrate to a fixed release.
7.6 and later	Not affected.
7.7 and later	7.10.1

Users of these products are recommended to upgrade to the latest version to fix this vulnerability and prevent them from getting exploited.

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