vim before patch 8.0.0322 does not properly validate values for tree length when handling a spell file, which may result in an integer overflow at a memory allocation site and a resultant buffer overflow.

References

• https://nvd.nist.gov/vuln/detail/CVE-2017-5953
• vim/vim@399c297
• https://groups.google.com/forum/#!topic/vim_dev/t-3RSdEnrHY
• https://security.gentoo.org/glsa/201706-26
• https://usn.ubuntu.com/4016-1/
• https://usn.ubuntu.com/4309-1/
• http://www.debian.org/security/2017/dsa-3786
• http://www.securityfocus.com/bid/96217