Fox News reports that before the U.S. Ambassador to Libya and three other Americans were killed in a terrorist attack in Benghazi on September 11, 2012, the Obama administration was running weapons through Benghazi to Banias and Borj Islam, Syria, and that “U.S. intelligence agencies were fully aware” of that:

US Intelligence agencies were fully aware that weapons were moving from the terrorist stronghold in Libya to Syria before the attack that killed four Americans…
September 16, 2012 DIA Memo copied to the National Security Council, CIA, and others concluded the Benghazi terrorist attack was planned at least ten or more days in advance…
The memo also tied the attack to 9-11… No discussion of a demonstration or anti-Mohammad video.
US officials were aware that weapons were being shipped to Syria by the Port of Benghazi.

Hillary Clinton repeatedly denied any knowledge of this. Here is one example from a transcript of Clinton being questioned on the matter by Senator Rand Paul:

Sen. Rand Paul: My question is, is the US involved in any procuring of weapons, transfer of weapons, buying, selling anyhow transferring weapons to Turkey out of Libya?
Hillary Clinton: To Turkey? I’ll have to take that question for the record. That’s, nobody’s ever raised that with me.
Sen. Rand Paul: It’s been in news reports that ships have been leaving from Libya and that they may have weapons. And what I’d like to know is, that annex that was close by, were they involved with procuring, buying, selling, obtaining weapons and were any of these weapons being transferred to other countries? Any countries, Turkey included?
Hillary Clinton: Well Senator, you’ll have to direct that question to the agency that ran the annex. And I will see what information was available.
Sen. Rand Paul: You’re saying you don’t know?
Hillary Clinton: I do not know. I don’t have any information on that.

http://www.truthrevolt.org/news/confirmation-us-was-running-weapons-through-benghazi-syria