There was an easily exploitable uncontrolled memory resource consumption denial-of-service vulnerability that existed in the peer-to-peer network code of three implementations of Bitcoin and several alternative chains.
For more details please see:
https://invdos.net/
For the paper:
https://invdos.net/paper/CVE-2018-17145.pdf
en.bitcoin.it/wiki/Common_Vulnerabilities_and_Exposures#CVE-2018-17145
github.com/bcoin-org/bcoin
github.com/bcoin-org/bcoin/security/advisories/GHSA-hx3r-jv9q-85jw
github.com/bitcoin/bitcoin/blob/v0.16.2/doc/release-notes.md
invdos.net
invdos.net/paper/CVE-2018-17145.pdf
nvd.nist.gov/vuln/detail/CVE-2018-17145