Cisco Security Advisory
IOS Reload after Scanning Vulnerability
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Security Scanning software can cause a memory error in Cisco IOS?? Software that will cause a reload to occur. This vulnerability affects only Cisco IOS software version 12.1(2)T and 12.1(3)T, and limited deployment releases based on those versions.
Customers using the affected Cisco IOS software releases are urged to upgrade as soon as possible to later versions that are not vulnerable to this defect. Vulnerable products and releases are listed in detail below.
The security scanner makes TCP connection attempts to various ports, looking for open ports to further investigate known vulnerabilities with those services associated with certain ports. However, a side effect of the tests exposes the defect described in this security advisory, and the router will reload unexpectedly as soon as it receives a request to review or write the configuration file.
This defect is documented as Cisco Bug ID CSCds07326.
The complete notice will be available at https://sec.cloudapps.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-20010524-ios-tcp-scanner-reload.
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This section provides details on affected products.
Vulnerable Products
It is impossible to list all Cisco products in this notice; the lists below include only the most commonly used or most asked-about products.
If you are unsure whether your device is running Cisco IOS software, log into the device and issue the command show version. Cisco IOS software will identify itself simply as "IOS" or "Internetwork Operating System Software". Other Cisco devices either will not have the show version command, or will give different output.
Cisco devices that run Cisco IOS software include the following:
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Cisco routers in the AGS/MGS/CGS/AGS+, IGS, RSM, 8xx, ubr9xx, 1xxx,
25xx, 26xx, 30xx, 36xx, 38xx, 40xx, 45xx, 47xx, AS52xx,
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AS53xx, AS58xx, 64xx, 70xx, 72xx (including the ubr72xx), 75xx, and
12xxx series.
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Most recent versions of the LS1010 ATM switch.
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Some versions of the Catalyst 2900XL LAN switch.
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The Cisco DistributedDirector.
The affected software versions are relatively new, and are not necessarily available on every device listed above.
Products Confirmed Not Vulnerable
If you are not running Cisco IOS software, you are not affected by this vulnerability. Cisco devices which do not run Cisco IOS software, and are not affected by this vulnerability, include the following:
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7xx dialup routers (750, 760, and 770 series) are not affected.
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Catalyst 19xx, 28xx, 29xx, 3xxx, and 5xxx LAN switches are not
affected, except for some versions of the Catalyst 2900XL. However, optional
router modules running Cisco IOS software in switch backplanes, such as the RSM
module for the Catalyst 5000 and 5500, are affected.
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WAN switching products in the IGX and BPX lines are not affected.
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The MGX (formerly known as the AXIS shelf) is not affected.
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No host-based software is affected.
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The Cisco PIX Firewall is not affected.
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The Cisco LocalDirector is not affected.
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The Cisco Cache Engine is not affected.
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The Cisco CSS 11000 series switch is not affected
No other Cisco products are currently known to be affected by these vulnerabilities.
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Cisco routers in the AGS/MGS/CGS/AGS+, IGS, RSM, 8xx, ubr9xx, 1xxx,
25xx, 26xx, 30xx, 36xx, 38xx, 40xx, 45xx, 47xx, AS52xx,
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An attempt to make a TCP connection to ports 3100-3999, 5100-5999, 7100-7999, and 10100-10999 will cause the router to unexpectedly reload at the next show running-config, or write memory, or any command that causes the configuration file to be accessed. Cisco IOS software cannot be configured to support any services that might listen at those port addresses, and cannot be configured to accept connections on those ports, however, connection attempts to these ports in the affected version will cause memory corruption, later leading to an unexpected reload.
Software packages are available from various commercial and free sites that perform automated remote tests for computer security vulnerabilities by scanning computers on a network for known security flaws. A common log message in environments that experienced security scan related crashes was the "attempt to connect to RSHELL" error message.
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Bug ID -- This problem was introduced in 12.1(1.3)T,
and is identified by Cisco Bug ID CSCds07326.
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Bug ID -- This problem was introduced in 12.1(1.3)T,
and is identified by Cisco Bug ID CSCds07326.
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This vulnerability can be mitigated by configuring access lists and applying access groups on all interfaces or on external devices or firewalls to prevent connection attempts to affected routers, and to eliminate router addresses in any planned security scanning exercises.
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This defect was introduced in version 12.1(1.3)T, and is repaired in the following versions which are based on the 12.1(2)T and 12.1(3)T releases.
The following table summarizes the Cisco IOS software releases that are known to be affected, and the earliest estimated dates of availability for the recommended fixed versions. Dates are always tentative and subject to change.
Each row of the table describes a release train and the platforms or products for which it is intended. If a given release train is vulnerable, then the earliest possible releases that contain the fix and the anticipated date of availability for each are listed in the "Rebuild", "Interim", and "Maintenance" columns. A device running any release in the given train that is earlier than the release in a specific column (less than the earliest fixed release) is known to be vulnerable, and it should be upgraded at least to the indicated release or a later version (greater than the earliest fixed release label).
When selecting a release, keep in mind the following definitions:
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Maintenance
Most heavily tested and highly recommended release of any label in a given row of the table.
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Rebuild
Constructed from the previous maintenance or major release in the same train, it contains the fix for a specific defect. Although it receives less testing, it contains only the minimal changes necessary to effect the repair.
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Interim
Built at regular intervals between maintenance releases and receive less testing. Interims should be selected only if there is no other suitable release that addresses the vulnerability, and interim images should be upgraded to the next available maintenance release as soon as possible. Interim releases are not available via manufacturing, and usually they are not available for customer download from CCO without prior arrangement with the Cisco TAC.
In the table below, the logical superseding software is recommended when there is no rebuild or maintenance planned for a specific software release. Customers should verify that planned upgrades will meet their requirements. For further details, see the IOS Release Notes for each Cisco IOS Train. http://www.cisco.com/univercd/cc/td/doc/product/software/index.htm. In all cases, customers should exercise caution to be certain the devices to be upgraded contain sufficient memory and that current hardware and software configurations will continue to be supported properly by the new release. If the information is not clear, contact the Cisco TAC for assistance as shown later in this notice.
More information on Cisco IOS Software release names and abbreviations is available at http://www.cisco.com/en/US/products/sw/iosswrel/tsd_products_support_category_home.html.
Major Release
Description or Platform
Availability of Repaired Releases*
Unaffected Earlier Releases
Rebuild
Interim**
Maintenance
12.0 and earlier, all variants
Numerous
Not vulnerable
Not vulnerable
Not vulnerable
12.1-based Releases
Rebuild
Interim**
Maintenance
12.1
General Deployment (GD) candidate: all platforms
Not vulnerable
Not vulnerable
Not vulnerable
12.1AA
Dial Support
Not vulnerable
Not vulnerable
Not vulnerable
12.1CX
Core/ISP support: GSR, RSP, C7200
Not vulnerable
Not vulnerable
Not vulnerable
12.1DA
xDSL Support: 6100, 6200
Not vulnerable
Not vulnerable
Not vulnerable
12.1DB
Cisco 6400 Universal Access Concentrator
12.1(4)DB
12.1DC
xDSL NRP support: c6400r
12.1(4)DC
12.1E
Core/ISP Support: GSR, RSP, c7200
Not vulnerable
Not vulnerable
Not vulnerable
12.1EC
Early Deployment (ED): ubr7200, UBR Headend platforms
Not vulnerable
Not vulnerable
Not vulnerable
12.1EX
Catalyst 6000
Not vulnerable
Not vulnerable
Not vulnerable
12.1EY
Catalyst 8510, 8540, LS1010
Not vulnerable
Not vulnerable
Not vulnerable
12.1T
New technology Early Deployment (ED): all platforms
12.1(4.3)T
12.1(5)T
12.1XA
Early Deployment (ED): limited platforms
Not vulnerable
Not vulnerable
Not vulnerable
12.1XB
Early Deployment (ED): limited platforms
12.2(1)
12.1XC
Early Deployment (ED): limited platforms
12.2(1)
12.1XD
Early Deployment (ED): limited platforms
Not vulnerable
Not vulnerable
Not vulnerable
12.1XE
Early Deployment (ED): limited platforms
12.2(1)
12.1XF
Early Deployment (ED): limited platforms
12.2(1)
12.1XG
Early Deployment (ED): limited platforms
12.2T***
12.1XH
Early Deployment (ED): limited platforms
12.2(1)
12.1XI
Early Deployment (ED): limited platforms
12.2(1)
12.1XJ
Early Deployment (ED): limited platforms
12.2T***
12.1XK
Early Deployment (ED): limited platforms
12.2(1)
12.1XL
Early Deployment (ED): limited platforms
12.2(1)
12.1XM
Early Deployment (ED): limited platforms
Not Vulnerable
Not Vulnerable
Not Vulnerable
12.1XP
Early Deployment (ED): limited platforms
12.2T***
12.1XQ
Early Deployment (ED): limited platforms
12.2T***
12.1XR
Early Deployment (ED): limited platforms
Not Vulnerable
Not Vulnerable
Not Vulnerable
12.1XS
Early Deployment (ED): limited platforms
12.1(5)XS
12.1XT
Early Deployment (ED): limited platforms
12.2T***
12.1XU
Early Deployment (ED): limited platforms
Not Vulnerable
Not Vulnerable
Not Vulnerable
12.1XV
Early Deployment (ED): limited platforms
Not Vulnerable
Not Vulnerable
Not Vulnerable
12.1XW
Early Deployment (ED): limited platforms
Not Vulnerable
Not Vulnerable
Not Vulnerable
12.1XX
Early Deployment (ED): limited platforms
Not Vulnerable
Not Vulnerable
Not Vulnerable
12.1XY
Early Deployment (ED): limited platforms
Not Vulnerable
Not Vulnerable
Not Vulnerable
12.1XZ
Early Deployment (ED): limited platforms
Not Vulnerable
Not Vulnerable
Not Vulnerable
12.1YA
Early Deployment (ED): limited platforms
Not Vulnerable
Not Vulnerable
Not Vulnerable
12.1YB
Early Deployment (ED): limited platforms
Not Vulnerable
Not Vulnerable
Not Vulnerable
12.1YC
Early Deployment (ED): limited platforms
Not Vulnerable
Not Vulnerable
Not Vulnerable
12.1YD
Early Deployment (ED): limited platforms
Not Vulnerable
Not Vulnerable
Not Vulnerable
Notes
* All dates are estimated and subject to change.
** Interim releases are subjected to less rigorous testing than regular maintenance releases, and may have serious bugs.
*** This release does not have a rebuild solution. Customers should upgrade to 12.2T when it becomes available. This is not a misprint.
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Maintenance
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The Cisco PSIRT is not aware of any public announcements or malicious use of the vulnerabilities described in this advisory. However, many reports of reloads related to this vulnerability have been reported by customers, due to customer use of security scanning software.
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To learn about Cisco security vulnerability disclosure policies and publications, see the Security Vulnerability Policy. This document also contains instructions for obtaining fixed software and receiving security vulnerability information from Cisco.
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Revision 1.1
2001-May-24
Made changes to the workarounds section
Revision 1.0
2001-May-24
Initial public release.
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