REXML is an XML toolkit for Ruby. The REXML gem before 3.3.9 has a ReDoS vulnerability when it parses an XML that has many digits between &# and x...; in a hex numeric character reference (&#x...;). This does not happen with Ruby 3.2 or later. Ruby 3.1 is the only affected maintained Ruby. The REXML gem 3.3.9 or later include the patch to fix the vulnerability.
https://www.ruby-lang.org/en/news/2024/10/28/redos-rexml-cve-2024-49761
https://github.com/ruby/rexml/security/advisories/GHSA-2rxp-v6pw-ch6m
https://github.com/ruby/rexml/commit/ce59f2eb1aeb371fe1643414f06618dbe031979f
Published: 2024-10-28
Updated: 2024-11-05
Base Score: 7.8
Vector: CVSS2#AV:N/AC:L/Au:N/C:N/I:N/A:C
Severity: High
Base Score: 7.5
Vector: CVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
Severity: High
Base Score: 8.7
Vector: CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N
Severity: High