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  4. Attack: Cisco IOS Unauth Admin Access

Attack: Cisco IOS Unauth Admin Access

Severity: High

This attack could pose a serious security threat. You should take immediate action to stop any damage or prevent further damage from happening.

Description

This signature detects an attempt to exploit a vulnerability in the Cisco IOS Administration Menu.

Additional Information

IOS is router firmware developed and distributed by Cisco Systems. IOS functions on numerous Cisco devices, including routers and switches.
A problem with the Cisco firmware makes it possible for a remote user to gain elevated privileges. This vulnerability can be exploited by attackers to gain full administrative access on the affect device, allowing a remote user to reconfigure devices using the affected firmware.
The problem is in the ability of a user to access the HTTP configuration menu of a Cisco device. A remote user accessing:
http://router.address/level/$NUMBER/exec/....
(where $NUMBER is a number in the range of 16 to 99) bypasses all authentication checking. This leads to a remote user gaining a privilege level of 15, which in IOS software is full administrative access (also known as enable).
With administrative access, remote attackers may be able to further compromise the network. They may be able to, for example: divert/redirect traffic, possibly monitor traffic, and/or cause a denial of service.

Affected

  • Cisco IOS 11.3, 11.3 AA, 11.3 DA, 11.3 DB, 11.3 HA, 11.3 MA, 11.3 NA, 11.3 T, 11.3 XA, 12.0, 12.0(10)W5(18g), 12.0(14)W5(20), 12.0(5)XK, 12.0(7)XK, 12.0 DA, 12.0 DB, 12.0 DC, 12.0 S, 12.0 SC, 12.0 SL, 12.0 ST, 12.0 T, 12.0 WC, 12.0 WT, 12.0 XA, 12.0 XB, 12.0 XC, 12.0 XD, 12.0 XE, 12.0 XF, 12.0 XG, 12.0 XH, 12.0 XI, 12.0 XJ, 12.0 XL, 12.0 XM, 12.0 XN, 12.0 XP, 12.0 XQ, 12.0 XR, 12.0 XS, 12.0 XU, 12.0 XV, 12.1, 12.1 AA, 12.1 CX, 12.1 DA, 12.1 DB, 12.1 DC, 12.1 E, 12.1 EC, 12.1 EX, 12.1 EY, 12.1 EZ, 12.1 T, 12.1 XA, 12.1 XB, 12.1 XC, 12.1 XD, 12.1 XE, 12.1 XF, 12.1 XG, 12.1 XH, 12.1 XI, 12.1 XJ, 12.1 XK, 12.1 XL, 12.1 XM, 12.1 XP, 12.1 XQ, 12.1 XR, 12.1 XS, 12.1 XT, 12.1 XU, 12.1 XV, 12.1 XW, 12.1 XX, 12.1 XY, 12.1 XZ, 12.1 YA, 12.1 YB, 12.1 YC, 12.1 YD, 12.1 YF, 12.2, 12.2 T, 12.2 XA, 12.2 XD, 12.2 XE, 12.2 XH, 12.2 XQ

Response

Workaround:
Disable the HTTP service on the device.
This vulnerability is not present when the Terminal Access Controller Access Control System (TACACS+) or Radius authentication systems are used. Enabling one of these authentication mechanisms in place of local authorization databases will prevent the vulnerability from being exploited. Information about enabling TACACS+ or Radius can be found in the following Cisco document:
TACACS+ Freeware for First-Time Users

Solution:
The following versions of IOS currently have no upgrade information yet:
12.0SL
12.0ST
12.0WC
12.0WT
See the Cisco advisory on this issue for more information.
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