A few months ago I was trying to PoC a known cross-site scripting vulnerability in the Cisco ASA WebVPN portal (CVE-2013-3414) for inclusion in the TrustKeeper Scan Engine. I tried a number of different techniques on multiple different ASA versions/branches and I simply could not tease out a viable PoC.
At my wits end, I finally decided to toss up a hail mary pass to my fellow Spiders for help. Thankfully, I received a reply from Piotr Karolak of the SpiderLabs Network Penetration team who PoC'd a cross-site scripting vulnerability during a customer pentest shortly after my request went out and it matched the vulnerability description.
According to Cisco, the vulnerability was described as follows:
So, when Piotr's PoC yielded the following reflected XSS on the WebVPN portal login page, we were quite sure that we had found the vulnerability:
After some testing we verified that our lab Cisco ASA reflected an XSS payload that executed Javascript in Internet Explorer 6.0 (more modern browsers were unaffected, thankfully). We then added a vulnerability check to the TrustKeeper Scan Engine and declared victory over CVE-2013-3414.
About a month later, our victory was short-lived when Heather Pilkington of the SpiderLabs Network Penetration team contacted me. She was performing a different penetration test and found this same vulnerability exposed on a fully patched Cisco ASA.
We then contacted Cisco PSIRT who confirmed that this particular vulnerability was actually a new vulnerability and was not CVE-2013-3414.
This meant that our vulnerability scanner was finding the vulnerability (a "zero-day" at the time) and popping up in customer vulnerability scan reports while we were working to responsibly disclose this vulnerability to Cisco PSIRT, which as you can imagine was far from ideal.
Thankfully, Cisco was really cool about the whole thing and quickly patched the vulnerability and issued a Cisco Security Advisory on March 18th:
http://tools.cisco.com/security/center/content/CiscoSecurityNotice/CVE-2014-2120
We have also drafted up a short Trustwave advisory to add a little more detail about the vulnerability:
Many thanks to Piotr Karolak, Heather Pilkington, and Cisco PSIRT for their awesome contributions as we worked through this rather abnormal vulnerability discovery and disclosure.