Advisory ID: cisco-sa-19980122-aaapair
For Public Release 1998 January 22 00:00 UTC (GMT)
A vulnerability (bug ID CSCdj74723) in AAA authentication processing on
Cisco IOS versions 11.3(1.2) and 11.3(1.2)T may allow users to get access for
which they are not intended to be authorized. This affects only the 11.3(1.2)
and 11.3(1.2)T interim releases. It does not affect any non-interim, production
Cisco IOS software release.
The bug that creates this vulnerability may also result in access
being denied to legitimate users, or in system crashes. If you are a
user and you have logged in, you can view bug details.
registered customers only)
The complete text of this advisory will be located at
All systems running Cisco IOS Software version 11.3(1.2) or 11.3(1.2)T,
and which use TACACS+, RADIUS, or other AAA services for authorization, are
affected by this vulnerability. If your configuration includes any command
beginning with "aaa authorization", then you are vulnerable. Systems using AAA
strictly for login authentication, as opposed to service authorization, and
systems using local authentication, are unaffected.
We believe that the most commonly affected configurations will be those
using TACACS+ or RADIUS servers.
Systems running engineering special releases containing the fix for bug
ID CSCdi51915 may also be affected. If you are a
user and you have logged in, you can view bug details.
registered customers only)
No other Cisco products are currently known to be affected by these
This vulnerability (Bug ID CSCdj74723) was introduced by the fix for
Bug ID CSCdi51915, which was integrated in Cisco IOS versions 11.3(1.2) and
11.3(1.2)T. It has been fixed for 11.3(1.3) and 11.3(1.3)T. Only these interim
releases are affected; CSCdj74723 is not in any regular, released Cisco IOS
Cisco's product security incident response team does not know of any
engineering specials that are vulnerable, but, because such specials may be
released on an informal basis, it is impossible to determine with absolute
certainty whether or not such images exist. Cisco personnel who have been
involved in the issuance of specials to customers since January 8, 1998, and
customers who have received such specials, are advised to check to make sure
that the fix for CSCdi51915 is not in their specials. If that fix is there, the
fix for CSCdj74723 must be added to protect against this vulnerability.
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
This vulnerability may let attackers evade authorization, which may
mean that they can issue system commands that they would not otherwise be able
to issue, or that they can make connections or send packets to destinations
that they would not otherwise be able to reach. It is possible for this to
happen without any special skills or knowledge on the part of the attacker, and
it is also possible for extra access to be granted to a legitimate user who
isn't deliberately conducting an attack at all. The effects of the
vulnerability depend on the installation, but you should assume that it opens
very broad access to your network.
The underlying bug can also result in denial of authorization to
legitimate users, or in system crashes.
When considering software upgrades, also consult
and any subsequent advisories to determine exposure and a complete upgrade
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 Technical
Assistance Center ("TAC") or your contracted maintenance provider for
There is no configuration workaround for this vulnerability, short of
completely disabling AAA authorization.
Cisco has made free software available to address this vulnerability
for affected customers. 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 Cisco.com Downloads at
Do not contact either "email@example.com" or "firstname.lastname@example.org"
for software upgrades.
Customers with contracts should obtain upgraded software through their
regular update channels. For most customers, this means that upgrades should be
obtained through the Software Center on Cisco's worldwide website at
Customers whose Cisco products are provided or maintained through prior
or existing agreement 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 who purchase direct from Cisco but who do not hold a Cisco
service contract and customers who purchase through third-party vendors but are
unsuccessful at obtaining fixed software through their point of sale should get
their upgrades 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)
Have your product serial number available and give the URL of this
notice as evidence of your entitlement to a free upgrade. Free upgrades for
non-contract customers must be requested through the TAC.
for additional TAC contact information, including special localized telephone
numbers and instructions and e-mail addresses for use in various
Cisco has had no known reports of malicious exploitation of this
Cisco knows of no public announcements of the existence of this
vulnerability before the date of this notice.
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The initial version of this notice is being sent to the customers that
our records show have downloaded the affected releases.
This notice will be posted in the "Field
Notices" section of Cisco's Worldwide Web site, which can be found under
"Technical Tips" in the "Software and Support" section. The URL is
The copy on the Worldwide Web will be updated as appropriate.
If there are future changes to this notice, the new versions will be
posted on the Worldwide Web. Updates will not be sent in e-mail unless the
changes are significant.
Initial public release.
Please report security issues with Cisco products, and/or sensitive
security intrusion emergencies involving Cisco products, to
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shortly be creating a security announcement mailing list for outgoing
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Please do not use email@example.com for configuration questions,
for security intrusions that you do not consider to be sensitive emergencies,
or for general, non-security-related support requests. We do not have the
capacity to handle such requests through this channel, and will have to refer
Technical Assistance Center, delaying response to your questions. We
advise contacting the Technical Assistance Center directly with such questions.