My question is about furthest object in the observable universe except Сosmic microwave background.
About 13.1 billion light years.
The z8 GND 5296 Galaxy mentioned in the article linked by TildalWave, mere 700 millions years old (after Big Bang) would be the mentioned distance from us for the light to reach us at indicated speed, considering the 13.798 bln years old universe. As we push technological barriers, we keep finding more distant objects.
The age of the universe is the hard limit in light years of distance of any observable object - there was nothing to emit light more than 13.798 bln years ago, or respectively,
visible from more than 13.798 bln light years away. visible from distance that what was 13.798 bln light years 13.798 bln years ago - or, after adjusting for universe expansion over that time, currently 46.6 billion light years away.
Of course, as RhysW mentions, this limit changes over time as the universe ages and grows. The exact rate of growth is 74.2km/sec per megaparsec, or about 0.000000007% per year. I'd say, comparing to our life and current technological progress, an insignificant factor.
There are few objects that might have even higher redshift. Googling I've found three accepted papers:
is about a strong lensed candidate at $z\approx11$ published on Astrophysical Journal
There are also few gamma ray burst associated with objects at large redshift. This database containts:
- z=8.26 GRB090423
- z=9.2 GRB090429B. The redshift if photometric, which means that the error on the determination is likely large
There might be few other around