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Cisco Security Advisory

"Code Red" Worm - Customer Impact

Advisory ID: cisco-sa-20010720-code-red-worm

Revision 2.3

For Public Release 2001 July 20 12:00  UTC (GMT)


A malicious self-replicating program known as the "Code Red" worm is targeted at systems running the Microsoft Internet Information Server (IIS). Several Cisco products are installed or provided on targeted systems. Additionally, the behavior of the worm can cause problems for other network devices.

The following Cisco products are vulnerable because they run affected versions of Microsoft IIS:

  • Cisco CallManager
  • Cisco Unity Server
  • Cisco uOne
  • Cisco ICS7750
  • Cisco Building Broadband Service Manager
  • IP/VC 3540 Application Server

Other Cisco products may also be adversely affected by the "Code Red" worm. Please see the Affected Products section for further details.

The worm and its effects may be remedied by applying the Microsoft patch to affected servers:

This advisory is available at

Affected Products

This section provides details on affected products.

Vulnerable Products

The following Cisco products are directly vulnerable because they run affected versions of Microsoft IIS:

  • Cisco CallManager
  • Cisco Unity Server
  • Cisco uOne
  • Cisco ICS7750
  • Cisco Building Broadband Service Manager
  • IP/VC 3540 Application Server

The following Cisco products may be vulnerable due to side-effects caused by the "Code Red" worm. They are not directly vulnerable to the Microsoft IIS exploit:

  • Cisco IP/VC 3510 H.323 Videoconference Multipoint Control Units
  • Cisco Aironet Wireless products
  • Cisco CSS 11000 series Content Service Switches
  • Cisco 600 Series of DSL routers that have not been patched for a previously published vulnerability
  • Cisco IP Phone 7960, 7940, 7910
  • CiscoSecure User Changeable Password software
  • Cisco WebView

The following Cisco products may be installed on various web servers and are vulnerable if installed on a Microsoft IIS server:

  • Cisco Collaboration Server (CCS)
  • Cisco Dynamic Content Adapter (DCA)
  • Cisco Media Blender (CMB)
  • TrailHead (Part of the Web Gateway solution)

Various Cisco Network Management products may be installed on Microsoft platforms that may be running a vulnerable version of IIS. Much older versions of CiscoWorks 2000 RWAN/CWSI Campus v2.x and Cisco Voice Manager v1.x are directly vulnerable because IIS was required as a part of the installation. Such systems might be offering HTTP services on default ports. These specific software packages are no longer supported, but are included in this notice to alert customers that might still be using them.

Products Confirmed Not Vulnerable

No other Cisco products are currently known to be affected by these vulnerabilities.


At least three versions of the "Code Red" worm are known to exist.

Both versions exploit a known vulnerability in Microsoft IIS by passing a specially crafted Uniform Resource Identifier (URI) to the default HTTP service, port 80, on a susceptible system. The URI in version 1 consists of binary instructions which cause the infected host to either begin scanning other random IP addresses and pass the infection on to any other vulnerable systems it finds, or launch a denial of service attack targeted at the IP address which, until very recently, was assigned to In both cases, the worm replaces the web server's default web page with a defaced page at the time of initial infection. Version 2 has the same behavior, except that it does not deface the default web page, and it no longer contains a hard-coded address for, opting instead to look up the address via DNS.

Version 1 does not produce a truly random list of addresses to attack, whereas version 2 contains a fixed randomizer that will attempt all possible IP addresses except those beginning with 127.x.x.x or 224.x.x.x. The worm does not check for pre-existing infection, so that any given system may be executing as many copies of the worm as have scanned it, with a compounding effect on system and network demand.

A newer variant named Code Red II is known to exploit the same vulnerability as the other Code Red strains, however the effects and damage to the local webserver are different. For more details, refer to the analysis of the worm at the following location:

Cisco products that are directly vulnerable because they use IIS can be protected from infection by applying the recommended patches from Microsoft. Workarounds are available as a temporary measure.

Side-effects caused by the worm can expose unrelated problems on other products. When the traffic from the worm reaches a significant level, a Cisco CSS 11000 series Content Service Switch may suffer a memory allocation error that leads to memory corruption and will require a reboot. The defect is documented in DDTS CSCdu76237. Traffic from the worm can trigger a defect in the IP/VC 3510 Videoconference Multipoint Control Unit which is documented in DDTS CSCdv01788. Traffic from the worm can trigger a defect in the Cisco Aironet Wireless devices, which is documented in DDTS CSCdv01662.

As a separate side-effect, the URI used by the worm to infect other hosts causes Cisco 600 series DSL routers to stop forwarding traffic. An affected 600 series router that has been scanned by the "Code Red" worm may not resume normal service until the power has been cycled.

The nature of the "Code Red" worm's scan of random IP addresses and the resulting sharp increase in network traffic can noticeably affect Cisco routers running Cisco IOS software, depending on the device, its current configuration, and the topology of the network. Unusually high CPU utilization and memory starvation may occur, and it can be mitigated in many cases simply by refining the configuration. Troubleshooting and configuration recommendations are available at this location:

Vulnerability Scoring Details

Cisco has provided scores for the vulnerabilities in this advisory based on the Common Vulnerability Scoring System (CVSS). The CVSS scoring in this Security Advisory is done in accordance with CVSS version 2.0.

CVSS is a standards-based scoring method that conveys vulnerability severity and helps determine urgency and priority of response.

Cisco has provided a base and temporal score. Customers can then compute environmental scores to assist in determining the impact of the vulnerability in individual networks.

Cisco has provided an FAQ to answer additional questions regarding CVSS at .

Cisco has also provided a CVSS calculator to help compute the environmental impact for individual networks at .


The "Code Red" worm is causing widespread denial of service on the Internet and is compromising large numbers of vulnerable systems. Any product or platform running a vulnerable version of Microsoft IIS may begin attempting to infect other systems with varying degrees of success, and may cause a significant increase in traffic load.

Once infected, the management of a Cisco CallManager product is disabled or severely limited until the defaced web page is removed and the original management web page is restored.

Cisco CSS 11000 Content Service Switches, Cisco IP/VC 3510 H.323 Videoconference Multipoint Control Units, Cisco Aironet Wireless Bridge/Access Point, Cisco IP phone models 7960, 7940, and 7910, and Cisco 600 series DSL routers are vulnerable to a repeatable denial of service until the software is upgraded, or workarounds are applied.

Software Versions and Fixes

Microsoft has made a patch available for affected systems at

Cisco is providing the same patch at

Documentation is available at

The Cisco Building Broadband Service Manager is documented separately at

The Cisco CSS 11000 Content Service Switch memory allocation error is fixed in versions R3.10 B78s, R4.01 B41s, R4.10 B21s, R5.0 B8s, and R5.01 B5.

Cisco is providing software patches for the IP/VC 3510 and IP/VC 3540 products at

The Cisco 67x series is vulnerable partially due to previously documented vulnerabilities at


We recommend following the instructions in the Microsoft security bulletin for addressing the actual vulnerability in IIS.

Workaround for CSS11000 Series Products

The memory allocation problem on the CSS 11000 Content Service Switches can be worked around by restricting XML access as shown:

restrict xml

Workaround for Cisco 600 Series Products

To disable web management on port 80, set the web management port to some number greater than 1024, and configure the web remote address for a non-routeable address.

set web port number_greater-than_1024
set web remote

Workaround for Cisco Aironet Wireless Bridge or Access Point: Disable Web Management

For the AP4800 series and Aironet Bridge devices, from the management console, select option 1 (Configuration Menu), then select option 4 (console menu), then check the setting of option 5 (Http). If setting is OFF, then web management is disabled. If setting is ON, select option 5 (Http) to toggle setting to OFF.

To avoid unnecessary handling of HTTP requests by Cisco routers running IOS, disable the HTTP server by applying:

no ip http server

while in global configuration mode. If HTTP service is needed, consider restricting access by applying an access list command.

Additional Workarounds for Handling "CodeRed" Traffic

Utilize the NBAR feature in supported Cisco IOS Software versions to aid in "Code Red" traffic identification and mitigation. This is discussed in detail at This workaround is applicable in Cisco IOS Software Version 12.1(5)T and later for many platforms.

Classify inbound Code Red traffic with the class-based marking feature in IOS.

Router(config)#class-map match-any http-codered
Router(config-cmap)#match protocol http url "*default.ida*"
Router(config-cmap)#match protocol http url "*cmd.exe*"
Router(config-cmap)#match protocol http url "*root.exe*"

Mark inbound Code Red traffic with a policy map.

Once the inbound traffic has been classified as Code Red, it can be marked with a specific DSCP. For this example, a decimal value of '1' is used as it is unlikely that any other traffic would be marked with this DSCP.

Router(config)#policy-map mark-inbound-http-codered
Router(config-pmap)#class http-codered
Router(config-pmap)#set ip dscp 1

Apply the service policy to the 'outside' interface so inbound traffic will be marked.

Router(config)#int e 0/0
Router(config-if)#service-policy input mark-inbound-http-codered

Block marked Code Red attempts with an ACL. The ACL will match on the DSCP value of '1' that was marked as the Code Red attempt entered in the box.

Router(config)#access-list 105 deny ip any any dscp 1 log
Router(config)#access-list 105 permit ip any any

Apply it outbound on the 'inside' interface where the target web servers are.

Router(config)#int e 0/1
Router(config-if)#ip access-group 105 out

Workaround for Cisco Cache/Content Engine Products

Additionally, Cisco Content Engines or Cisco Cache Engines can be configured to block "Code Red" associated traffic with a filter ruleset as described below.

Cache Engine/Content Engine

rule enable
rule block url-regex .*\.ida.*

Obtaining Fixed Software

Cisco has released software updates that address these vulnerabilities. Prior to deploying software, customers should consult their maintenance provider or check the software for feature set compatibility and known issues specific to their environment.

Customers may only install and expect support for the feature sets they have purchased. By installing, downloading, accessing or otherwise using such software upgrades, customers agree to be bound by the terms of Cisco's software license terms found at , or as otherwise set forth at Downloads at .

Do not contact or for software upgrades

Customers with Service Contracts

Customers with contracts should obtain software through their regular update channels. For most customers, software patches and bug fixes should be obtained through the Software Center on Cisco's worldwide website at

Customers Using Third-Party Support Organizations

Customers whose Cisco products are provided or maintained through prior or existing agreements with third-party support organizations, such as Cisco Partners, authorized resellers, or service providers should contact that support organization for guidance and assistance with the appropriate course of action in regards to this advisory.

The effectiveness of any workaround or fix is dependent on specific customer situations, such as product mix, network topology, traffic behavior, and organizational mission. Due to the variety of affected products and releases, customers should consult with their service provider or support organization to ensure any applied workaround or fix is the most appropriate for use in the intended network before it is deployed.

Customers Without Service Contracts

Customers who purchase direct from Cisco but do not hold a Cisco service contract, and customers who purchase through third-party vendors but are unsuccessful in obtaining fixed software through their point of sale should obtain software patches and bug fixes by contacting the Cisco Technical Assistance Center (TAC). TAC contacts are as follows.

  • +1 800 553 2447 (toll free from within North America)
  • +1 408 526 7209 (toll call from anywhere in the world)
  • e-mail:

Customers should have their product serial number available and be prepared to give the URL of this notice as evidence of entitlement to a software patch or bug fix. Customers without service contracts should request a software patch or bug fix through the TAC.

Refer to for additional TAC contact information, including localized telephone numbers, and instructions and e-mail addresses for use in various languages.

Exploitation and Public Announcements

This issue is being exploited actively and has been discussed in numerous public announcements and messages. References include:

The additional workarounds in this advisory utilizing the NBAR feature have been provided through the work of Randall Benn.

Status of This Notice: Final


A stand-alone copy or Paraphrase of the text of this document that omits the distribution URL in the following section is an uncontrolled copy, and may lack important information or contain factual errors.


This advisory is posted on Cisco's worldwide website at:

In addition to worldwide web posting, a text version of this notice is clear-signed with the Cisco PSIRT PGP key and is posted to the following e-mail and Usenet news recipients.


Future updates of this advisory, if any, will be placed on Cisco's worldwide website, but may or may not be actively announced on mailing lists or newsgroups. Users concerned about this problem are encouraged to check the above URL for any updates.

Revision History

Revision 2.3


Updated Additional Workarounds for Handling "CodeRed" Traffic section

Revision 2.2


Updated Workaround section and Affected Products

Revision 2.1


Updated Workaround section and Affected Products

Revision 2.0


Updated to include CSS 11000 and old network management platforms.

Revision 1.1


Made Microsoft patch URL visible, and changed relative links to fully qualified.

Revision 1.0


Initial public release.

Cisco Security Procedures

Complete information on reporting security vulnerabilities in Cisco products, obtaining assistance with security incidents, and registering to receive security information from Cisco, is available on Cisco's worldwide website at This includes instructions for press inquiries regarding Cisco security notices. All Cisco security advisories are available at

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