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[R2] Cisco IOS Smart Install Client Feature Config / Boot Image File List Upload Remote Code Execution

High

Synopsis

In 2013, Tenable Network Security reported a file upload remote code execution flaw in Cisco IOS Smart Install Client via the Zero Day Initiative (ZDI), tracked by Cisco as CSCub55790. Based on subsequent testing, it appears this issue was not fully fixed in the patches released by Cisco. Cisco 2960G switches running c2960-lanbasek9-mz.150-2.SE8.bin (compiled on 14-May-15) are still vulnerable.

This vulnerability allows the attacker to replace the startup configuration file and the booting IOS image on Cisco switches running as a Smart Install client. The attacker can specify a user account with highest access in the config file, allowing her to take complete control of the switch. The attacker can also upload a custom IOS image with backdoors in it. If the attacker specifies an non-existent image list file or IOS image tar file(s) in the image list file, the IOS image file(s) will not be uploaded. In this case, the attacker-specified config file will still be uploaded to the switch, and that config file will be used as the startup config file on next reboot using the existing IOS image.

Based on testing, the fix in cisco-sa-20130327-smartinstall only addresses the IOS crash/reload caused by malformed content in the image list file. It does not prevent an attacker from uploading an attacker-specified config file to the switch. Moreover, if the attacker specifies a valid IOS image in the image list file, that image will be uploaded and the switch will reboot using that image and the attacker-specified config file.

Note: Tenable asked Cisco to assign a CVE ID on 8/20/2015. An assignment was given to us from Cisco on 8/25/2015 of CVE-2015-6264. When the Cisco advisory was published on 3/23/2016, it used CVE-2016-1349. As such, that is a duplicate assignment and further does not follow CNA standards, as the ID should be issued based on the year it was discovered/reported, not disclosed. MITRE has opted to REJECT CVE-2015-6264 per their policy as CVE-2016-1349 "is the most commonly referenced identifier".

Solution

Cisco has released "free software updates that address the vulnerability". Consult the cisco-sa-20160323-smi advisory for details.

Disclosure Timeline

2015-06-23 - Informed vendor of first issue (RCE) via PSIRT email
2015-06-23 - Vendor acknowledged e-mail. States it is intended functionality, Cisco is looking into adding authentication to feature.
2015-07-02 - Informed vendor of second issue (DoS)
2015-07-02 - Vendor acknowledged e-mail, agrees it is an issue, opened PSIRT-0306179306
2015-08-11 - Pinged vendor on status
2015-08-11 - Vendor confirms fix in works, CSCuv45410 assigned
2015-08-21 - Tenable asks Cisco for CVE assignment, since they are a CNA
2015-08-25 - Cisco assigns CVE for tracking, per Tenable request
2015-11-24 - Tenable pings vendor for update
2015-12-10 - Tenable pings vendor for update
2015-12-10 - Cisco responds, after questioning them about CVE assignments and general security policy re: vulnerability disclosure. Replies saying they are "planning to disclose this through our biannual IOS bundle in March"
2016-03-23 - Vendor releases fix for issue, does not notify Tenable
2016-03-28 - Ping vendor for update
2016-03-28 - Vendor provides link to advisory, showing fix released 2016-03-23

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