A CERT az alábbi CISCO IOS-beli DoS jellegű sebezhetőségre hívta fel a figyelmet, ami a használt Cisco eszközök elég széles körét érinti:CERT® Advisory CA-2003-15 Cisco IOS Interface Blocked by IPv4 Packet
Original release date: July 16, 2003
Last revised: --
Source: CERT/CC
A complete revision history can be found at the end of this file.
Systems Affected
* All Cisco devices running Cisco IOS software and configured to process Internet Protocol version 4 (IPv4) packets
Overview
A vulnerability in many versions of Cisco IOS could allow an intruder to execute a denial-of-service attack against a vulnerable device.
I. Description
Cisco IOS is a very widely deployed network operating system. A vulnerability in IOS could allow an intruder to execute a denial-of-service attack against an affected device. Cisco has published an advisory on this topic, available at http://www.cisco.com/warp/public/707/cisco-sa-20030717-blocked.shtml We strongly encourage sites using IOS to read this document and take appropriate action.
The CERT/CC is tracking this issue as VU#411332. This reference number corresponds to CVE candidate CAN-2003-0567.
II. Impact
By sending specially crafted IPv4 packets to an interface on a vulnerable device, an intruder can cause the device to stop processing packets destined to that interface. Quoting from Cisco's advisory:
"A device receiving these specifically crafted IPv4 packets will force the inbound interface to stop processing traffic. The device may stop processing packets destined to the router, including routing protocol packets and ARP packets. No alarms will be triggered, nor will the router reload to correct itself. This issue can affect all Cisco devices running Cisco IOS software. This vulnerability may be exercised repeatedly resulting in loss of availability until a workaround has been applied or the device has been upgraded to a fixed version of code."
III. Solution
Apply a patch from Cisco
Apply a patch as described in Cisco's Advisory.
Until a patch can be applied, you can mitigate the risks presented by this vulnerability by judicious use of access control lists (ACLs). The correct use of ACLs depends of your network topology. Additionally, ACLs may degrade performace on some systems. We recommend reviewing the following before applying ACLs
http://www.cisco.com/warp/public/707/cisco-sa-20030717-blocked.shtml#workarounds
http://www.cisco.com/warp/public/707/racl.html
http://www.cisco.com/warp/public/707/iacl.html
The CERT Coordination Center thanks Cisco Systems of for notifying us about this problem and for helping us to construct this advisory.
Feedback about this advisory may be directed to the author, Shawn Hernan
This document is available from: http://www.cert.org/advisories/CA-2003-15.html