HIGH
The URL percent-encoding decode function in libcurl before 7.51.0 is called `curl_easy_unescape`. Internally, even if this function would be made to allocate a unscape destination buffer larger than 2GB, it would return that new length in a signed 32 bit integer variable, thus the length would get either just truncated or both truncated and turned negative. That could then lead to libcurl writing outside of its heap based buffer.
http://www.oracle.com/technetwork/security-advisory/cpuoct2018-4428296.html
http://www.securityfocus.com/bid/94105
http://www.securitytracker.com/id/1037192
https://access.redhat.com/errata/RHSA-2018:2486
https://access.redhat.com/errata/RHSA-2018:3558
https://bugzilla.redhat.com/show_bug.cgi?id=CVE-2016-8622
https://curl.haxx.se/docs/adv_20161102H.html
Source: MITRE
Published: 2018-07-31
Updated: 2018-11-13
Type: CWE-787
Base Score: 7.5
Vector: AV:N/AC:L/Au:N/C:P/I:P/A:P
Impact Score: 6.4
Exploitability Score: 10
Severity: HIGH
Base Score: 9.8
Vector: CVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
Impact Score: 5.9
Exploitability Score: 3.9
Severity: CRITICAL