That Vulnerability is “Theoretical”!

A few days ago, while writing a draft of a different blog, I made reference to and said “we’re well aware of the pitfalls around calling a vulnerability ‘theoretical’“! I wanted to link off to what I was referencing, a case where security researchers found a vulnerability in a big vendor’s products and were told it was “theoretical”. Of course, they in turn provided a working exploit for the vulnerability proving it wasn’t just theory. Thus, around 1995, the researchers took on the slogan “L0pht, Making the theoretical practical since 1992.” After digging, I couldn’t find a concise story of the details around that event, so I took to Twitter. Over the course of a couple hours, with input from many people, including some involved with the story, I collected the details. I told those in the conversation that if I had the information I would blog about it to better preserve that slice of history.

My bad memory had me believing the vulnerability was in Sendmail, and that Eric Allman said it to Mudge. Royce Williams dug up the Sendmail exploit i was thinking of, and the header text from Mudge suggested I was on the right track.

*NIX Sendmail (8.7.5) – Buffer Overflow – Newest sendmail exploit
:
# Hrm… and Eric Allman told me to my face that there were *no* buffer
# overflows in 8.7.5 — .mudge
# This works on systems that have the chpass program runable by
# users. Tested on FreeBSD, though the vulnerability exists in all
# Sendmail8.7.5. Granted you need to be able to change your gecos field 😉
#
# The problem is in buildfnam() which lives in util.c – it treats
# the static allocated array nbuf[MAXSIZE+1], from recipient.c, in
# an unbounded fashion.

Next, Royce reminded me that I had actually referenced that vulnerability in a prior blog post from 2006… oops! Mark Dowd was the first to challenge me on that, saying he believed it was related to a vulnerability in Microsoft’s products, related to RAS or CHAP, and he was right about the vendor (which vuln it was specifically is still not confirmed). Next, Space Rogue, an original L0pht member chimed in saying he thought it referred to Microsoft and the NT/Lanman vulnerability, and that the 1992 part of the slogan simply referred to when L0pht was formed. DKP further confirmed this by digging into the wonderful Internet Archive, finding the slogan and quote on the L0pht’s page.

“That vulnerability is completely theoretical.” — Microsoft
L0pht, Making the theoretical practical since 1992.

From here, Weld Pond and Mudge, original members of the L0pht joined the conversation. First, Weld said it might be a RAS or CHAP vulnerability but he wasn’t certain, but that the slogan came from a response from a Microsoft spokesperson who was quoted saying “that vulnerability is theoretical“, and that resulted in the exploit being written to prove otherwise. Weld further confirmed what Space Rogue had said, that the “slogan was coined in 95 or so but made retrospective to the founding of the L0pht.

DKP continued digging and found the quoted in Bruce Schneier’s “Secrets and Lies”, and pointed out Schneier worked with Mudge on a MS-CHAPv2 vulnerability. The paper on that vuln is from 1999 though, suggesting it wasn’t the “theoretical” vuln.

With that, the “theoretical” vulnerability is mostly uncovered. It would be great if anyone could confirm exactly which vulnerability it was that prompted the response from Microsoft. If anyone else recalls details about this, please share!

In the mean time, we also get to wonder about the Sendmail story, where this saga started, that also apparently is interesting. Space Rogue mentioned there was a separate story around that, but couldn’t remember details. Mudge jumped in confirming it was a Sendmail 8.6.9 exploit, “in response to in-person ‘discussion’ w/ [Eric] Allman at a Usenix Security in Texas. Witnesses, but no writeup.Mudge added that “a very similar ‘quote’ happened in person with Allman quite some time prior to the MS issue. It wasn’t a throw away quote. I/we lived it 🙂

August 14, 2017 Update:

Mudge provided more insight into another issue, also a ‘theoretical’ risk. During the Twitter thread, there were questions about L0phtcrack. Mudge saysIn a nutshell – a MSFT PR article in NT magazine said l0phtcrack was a theoretical risk but not an actual one. I responded with LC rant. Soon after we coined the phrase to describe the PoCs I felt it was crucial to write and release“. DKP dug up a Wired article that better illustrates how vendors can dismiss security researchers:

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