Impact
The REXML gem before 3.3.6 has a DoS vulnerability when it parses an XML that has many deep elements that have same local name attributes.
If you need to parse untrusted XMLs with tree parser API like REXML::Document.new, you may be impacted to this vulnerability. If you use other parser APIs such as stream parser API and SAX2 parser API, this vulnerability is not affected.
Patches
The REXML gem 3.3.6 or later include the patch to fix the vulnerability.
Workarounds
Don't parse untrusted XMLs with tree parser API.
References
https://www.ruby-lang.org/en/news/2024/08/22/dos-rexml-cve-2024-43398/ : An announce on www.ruby-lang.org
Impact
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. Note that Ruby 3.1 will reach EOL on 2025-03.
Patches
The REXML gem 3.3.9 or later include the patch to fix the vulnerability.
Workarounds
Use Ruby 3.2 or later instead of Ruby 3.1.
References
https://www.ruby-lang.org/en/news/2024/10/28/redos-rexml-cve-2024-49761/: An announce on www.ruby-lang.org
Impact
The REXML gems from 3.3.3 to 3.4.1 have a DoS vulnerability when parsing XML containing multiple XML declarations. If you need to parse untrusted XMLs, you may be impacted to these vulnerabilities.
Patches
REXML gems 3.4.2 or later include the patches to fix these vulnerabilities.
Workarounds
Don't parse untrusted XMLs.
References
https://www.ruby-lang.org/en/news/2025/09/18/dos-rexml-cve-2025-58767/ : An announcement on www.ruby-lang.org
A flaw was found in the way the Ruby REXML library parsed XML documents. Parsing a specially crafted XML document using REXML and writing parsed data back to a new XML document results in creating a document with a different structure. This issue could affect the integrity of processed data in applications using REXML that parse XML documents, write data back to XML, and re-parse them again.
Impact
The REXML gem before 3.3.2 has a DoS vulnerability when it parses an XML that has many entity expansions with SAX2 or pull parser API.
If you need to parse untrusted XMLs with SAX2 or pull parser API, you may be impacted to this vulnerability.
Patches
The REXML gem 3.3.3 or later include the patch to fix the vulnerability.
Workarounds
Don't parse untrusted XMLs with SAX2 or pull parser API.
References
https://www.ruby-lang.org/en/news/2008/08/23/dos-vulnerability-in-rexml/ : This is a similar vulnerability https://www.ruby-lang.org/en/news/2024/08/01/dos-rexml-cve-2024-41946/: An announce on www.ruby-lang.org
Impact
The REXML gem before 3.2.6 has a DoS vulnerability when it parses an XML that has many <s in an attribute value.
If you need to parse untrusted XMLs, you may be impacted to this vulnerability.
Patches
The REXML gem 3.2.7 or later include the patch to fix this vulnerability.
Workarounds
Don't parse untrusted XMLs.
References
https://www.ruby-lang.org/en/news/2024/05/16/dos-rexml-cve-2024-35176/
Impact
The REXML gem before 3.3.2 has some DoS vulnerabilities when it parses an XML that has many specific characters such as whitespace character, >] and ]>.
If you need to parse untrusted XMLs, you may be impacted to these vulnerabilities.
Patches
The REXML gem 3.3.3 or later include the patches to fix these vulnerabilities.
Workarounds
Don't parse untrusted XMLs.
References
https://github.com/ruby/rexml/security/advisories/GHSA-vg3r-rm7w-2xgh : This is a similar vulnerability https://github.com/ruby/rexml/security/advisories/GHSA-4xqq-m2hx-25v8 : This is a similar vulnerability https://www.ruby-lang.org/en/news/2024/08/01/dos-rexml-cve-2024-41123/: An announce on www.ruby-lang.org
Impact
The REXML gem before 3.3.1 has some DoS vulnerabilities when it parses an XML that has many specific characters such as <, 0 and %>.
If you need to parse untrusted XMLs, you may be impacted to these vulnerabilities.
Patches
The REXML gem 3.3.2 or later include the patches to fix these vulnerabilities.
Workarounds
Don't parse untrusted XMLs.
References
https://github.com/ruby/rexml/security/advisories/GHSA-vg3r-rm7w-2xgh : This is a similar vulnerability https://www.ruby-lang.org/en/news/2024/07/16/dos-rexml-cve-2024-39908/