Squid is a caching proxy for the Web. In versions 6.3 and below, Squid is vulnerable to a heap buffer overflow and possible remote code execution attack when processing URN due to incorrect buffer management. This has been fixed in version 6.4. To work around this issue, disable URN access permissions.
Exploitability
AV:NAC:LPR:NUI:NScope
S:CImpact
C:NI:LA:H9.3/CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:N/I:L/A:HOther