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GHSA-wjv4-x9w8-wm3h
No affected components available
Summary
Nokogiri::XML::Document#root= validated only that the new root was a Nokogiri::XML::Node, allowing a DTD node to be set as the document root. The result is a heap use-after-free during garbage collection or finalization, leading to an invalid memory read or potentially a segfault.
Nokogiri 1.19.4 restricts Document#root= to element nodes, raising TypeError for any other node type.
This memory-safety issue affects only the CRuby implementation (libxml2). The JRuby implementation was not affected; the same input validation was added there for behavioral parity.
Severity
The Nokogiri maintainers have evaluated this as low severity. This is only triggered by a programming error. It requires application code to assign a non-element node such as a DTD as the document root via Document#root=. Nokogiri 1.19.4 now raises TypeError instead of allowing a use-after-free. It cannot be triggered by untrusted input or through normal use of the public API.
Mitigation
Upgrade to Nokogiri 1.19.4 or later.
As a workaround, applications that cannot upgrade should avoid assigning a DTD (or any non-element node) via Document#root=.
Credit
This issue was responsibly reported by Zheng Yu from depthfirst.com.
The vulnerability can be exploited over the network without needing physical access. It is easy for an attacker to exploit this vulnerability. An attacker does not need any special privileges or access rights. No user interaction is needed for the attacker to exploit this vulnerability.
Limited exploitation activity has been observed. Close monitoring and planned remediation are recommended.
The exploit probability is very low. The vulnerability is unlikely to be exploited in the next 30 days.
We did not find any exploit available. Neither in GitHub repositories nor in the Exploit-Database.
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