The only open international border between Tajikistan and the Wakhan is located at Eshkashem. From Tajikistan into Afghanistan, you just need to hold a valid Afghan visa. From Afghanistan into Tajikistan, in addition to a valid Tajik visa, you need to request a permit to visit Gorno-Badakhshan Autonomous Oblast (known as GBAO permit) as it is a restricted area. See here.
There is at least one border crossing between Afghanistan and Tajikistan in the area of Ghund Ji Boi in the northwestern part of the Little Pamir (on the Tajik side, the border is called Kyzylrabot). An old road even runs between Tajikistan and Afghanistan until Bozai Gumbaz. It was used by the USSR troops during the invasion. The French film-maker Karel Prokop (L'Empire des Montagnes) travelled across the Afghan/Tajik border into Afghanistan by car. Mark Jenkins from Outside Magazine also crossed the pass illegally into Tajikistan in May 2005. They quickly got caught by the border police, spent 5 days in custody and were eventually released under the custody of the US embassy in Dushambe.
Crossing borders illegally is not recommended for three reasons:
If you really want to cross an officially closed international border, you need to get permit from the two countries to get through.
There are other border crossings between the two countries (in Qala-e-Panj and around Lake Zor Kol) that are officially closed.
There are several passes between the Wakhan and Pakistan, including the Boroghil Pass and the Dilisang pass. Officially, it is absolutely forbidden to cross the border from Afghanistan into Pakistan at either of the two passes. Some foreigners have tried to cross the border illegally in the past and have been sent to jail in Pakistan. In practice, holding the appropriate permit from the Pakistani authorities, it may possible to do so as John Mock and Kimberley O’Neil did so in 2004 (see their report).
There is another pass to Pakistan located between the Boroghil Pass and the Dilisang Pass called Irshad Uween. This pass was used by Philippe Valéry as mentioned in his book Par les sentiers de la soie: à pied jusqu'en Chine. In the summer of 2005 at least 2 international teams crossed the Irshad Uween pass into Pakistan. They had previously managed to get a special permit from Pakistani authorities.
A French traveler managed to cross the Boroghil Pass eastwards into Pakistan in the summer of 2004. However, it was possible because he had a high-ranking contact in Islamabad.
Traveling from Pakistan into Afghanistan may be possible but has probably never been tempted for at least a couple of decades. Afghan border authorities in Eshkashem confirmed
to us that they would let foreigners into the Wakhan coming from Pakistan via the Boroghil Pass. However, it is highly advisable to request a special permit. Note that even if Afghan authorities may let foreigners in at Boroghil pass, the pass is not considered as an open border in Pakistan and crossing it in either way is strictly prohibited from their perspective.
There is absolutely no way to travel inland between Afghanistan and China. The area eastwards beyond the China-Afghanistan border is a military zone that is strictly off-limit to any travelers, whether locals or foreigners. It is however possible to hike to the Waghjir Pass and to the Tegerman Su Pass.
See road map here.
Kabul to Faizabad
Although it may be possible, by starting before dawn, to cover the Kabul-Faizabad trip in a single day, it is safer to allow two days and stop in Kunduz, or better, in Taloqan for the night. The road is paved and in excellent condition between Kabul and Kunduz (via the Salang tunnel and Pol-e-Khomry). The road is paved and relatively in good condition between Kunduz and Taloqan. Beyond Taloqan, it is an extremely uncomfortable dirt road full of pot holes. In Kabul you can either hire your own taxi to get to Kunduz (50-60 USD) or take public transportation. All cars and public transportation to Kunduz and Faizabad leave from Sarai-Shamali in the north of Kabul. The journey to Kunduz takes 6-7 hours. Then add 1-2 hours to Taloqan. From Kunduz or Taloqan to Faizabad, allow a full day by taxi or public transportation (a Town Ace costs around 100 USD).
Faizabad to Eshkashem
In Faizabad, you can either hire your own car or try to take public transportation to go further east. Hiring your own car will (hopefully) allow you to travel directly at least to Qala-e-Panj and at best to Sarhad-e-Boroghil if road conditions allow it. Although it may be possible to cover the trip between Faizabad and Sarhad-e-Boroghil in 2 days, it is better to allow at least three days (one day to Eshkashem, one day to Khandud or Qala-e-Panj and one day to Sarahd-e-Boroghil). In Faizabad, allow a day to find a car (must be 4-wheel drive, pick up or Russian jeep) and an experienced driver. Make sure the driver knows the way and has experience in driving on flooded roads. Car hire will cost you 120-150 USD/day. You will need to pay for the return trip. In Faizabad, it is a good idea (but not essential) to introduce yourself to the local wali (governor).
Alternatively, you may use public transportation and/or hitch-hiking. From Faizabad, first go to Baharaq (2-hour drive). Cars to Baharaq leave between 5 and 6 AM. From Baharaq, find a car to Eshkashem (6-7 hours drive minimum). There are always a few cars (pick up, Town Ace, Russian jeep, NGO, etc.) that travel back and forth between Baharaq and Eshkashem.
Eshkashem to Khandud/Qala-e-Panj
Eshkashem is the town that controls the entrance to the Wakhan and is a compulsory 1-day stop. In Eshkashem, you MUST meet with the local commander and get permission to travel further east. Try NOT to be in Eshkashem on a Thursday or a Friday as the commander is sometimes away from town. Insist on getting a laissez-passer from the commander that stipulates Wakhan AND Pamir. See here for more details.
The road between Eshkashem and Qala-e-Panj and beyond was constructed in the 1950s-60s. It was in very poor condition until the mid-1990s, but has been much improved as far as Qala-e-Panj in recent years. It remains nonetheless a four-wheel-drive road annually destroyed by the floods where it crosses the innumerable flood 'washes'.
Allow a full day to complete the red-tape and find transportation to Qala-e-Panj. The next town after Eshkashem is Qazde where the local Shah resides (Shah Langar). Further on, the next major town is Khandud, where there is a clinic. There are a couple of cars in Khandud and this is your last chance to hire one to go further east. Depending on the level of water in the river, it is sometimes not possible to travel between Khandud and Qala-e-Panj other than in early morning. Ask in Khandud for more information. Qala-e-Panj is 1-2 hours beyond Khandud depending on the river flow.
Khandud/Qala-e-Panj to Sarhad-e-Boroghil
Although it is possible to cover the Khandud-Sarhad-e-Boroghil trip in one day if road conditions allow it and if you start from Khandud in early morning, it is a good idea to spend the night at the house of Shah-e-Panj, the local ismaili leader in Qala-e-Panj. At least try to pay him a visit. Qala-e-Panj lies at the Wakhan Corridor's westernmost point (also the widest point) and has a beautiful setting. It is there where the Panj river (Amu Daria) and the Wakhan river gather together to form the Oxus.
The road beyond Qala-e-Panj is accessible only when the river flow is not too strong. Many if the streams in this region that flow into the Wakhan river have no bridges and must be carefully navigated. It is important to be aware that, whatever people say, you will never be completely guaranteed to be able to travel by road all the way to Sarhad-e-Boroghil as some parts of the road are sometimes completely washed away by floods. Your car may be stopped by floods anywhere between Khandud and Sarhad and you may have to continue on foot or on horseback. Alternatively, you may decide to hire mules or horses in Qala-e-Panj and start walking from there. It is a 3-day walk between Qala-e-Panj and Sarhad-e-Boroghil, a good acclimatization hike before climbing up the Pamir.
During our 2005 trekking trip to the Wakhan, our car was stopped by floods near the village of Aogarch, a few kilometers beyond Qala-e-Panj eastwards. The road to Sarhad-e-Boroghil became accessible probably around mid-July. But it really depends on the year and whether there was a lot of snowfall during the winter.
Alternatively, you may want to get directly into the Big Pamir via Ghaz Khan, Ouezet or Sargaz. In this case, you will need to either to stop your car in Qala-e-Panj and start walking from there or push to Sost (starting point of the route to Ghaz Khan and the Big Pamir), Ouezet or Sargaz. Donkeys may be hired in Sost, Ghaz Khan or Ouezet. Probably not in Sargaz. Better: buy them for 200 USD/each.
See road map here.