This month's cryptocurrency boom isn't limited to bitcoin. Over the last 24 hours, two of bitcoin's biggest rivals—Litecoin and Ethereum's ether—have enjoyed huge price gains.

Trading volume has been so intense that one of the leading cryptocurrency exchange services, Coinbase, has suffered downtime.

"Ethereum buys and sells are temporarily disabled," read a notice on the Coinbase status page around 2pm Eastern time. That issue was resolved around 45 minutes later, while trading in litecoins was disabled for about 90 minutes earlier in the day. The status page lists both ether and litecoin trading as having a "Major Outage."

Bitcoin's price has also been doing well over the last 24 hours—but those gains were largely regaining ground lost over the weekend. Bitcoin recently passed $17,000, roughly the same value the currency reached last Thursday.

Over that same four-day period, ether's value has risen 35 percent, from $450 to $620. Ether is the currency of Ethereum, a blockchain-based network that offers a Turing-complete virtual machine that allows people to run computer programs called smart contracts.

Litecoin has soared an astonishing 150 percent in four days, from $130 to $325. Litecoin is one of the Internet's first "altcoins." It has features similar to bitcoin but is able to confirm transactions more quickly.

The rising price of litecoin and ether is part of a broader cryptocurrency boom. CoinMarketCap, a handy database of cryptocurrency prices, shows almost every cryptocurrency in the green over the last 24 hours, with many posting double-digit gains.

One possible explanation: publicity about bitcoin has drawn in a lot of new investors, but some have been concerned about how congestion on the bitcoin network has pushed up transaction fees to more than $20. The Litecoin network, by contrast, currently charges around $0.25 to perform a transaction. So people who are interested in cryptocurrencies but worried about bitcoin's limited throughput might be looking for other places to put their money.