Published: 13 December 2016
PCRE 7.8 and 8.32 through 8.37, and PCRE2 10.10 mishandle group empty matches, which might allow remote attackers to cause a denial of service (stack-based buffer overflow) via a crafted regular expression, as demonstrated by /^(?:(?(1)\\.|([^\\\\W_])?)+)+$/.
CVSS 3 base score: 7.5
This might be disputed, Tavis says it is likely php misusing the pcre3 API. I suspect allowing attackers to supply regular expressions is always going to be a bad idea.
upsteam bug says this is an issue with php, and are not going to fix, so marking this as not-affected