CVE-2026-13401 in XML::Bare
Summary
by MITRE • 07/16/2026
XML::Bare versions through 0.53 for Perl will hang in an infinite loop when parsing malformed attributes.
The parserc_parse function never advances the attribute-parse state cursor on certain malformed attribute forms, looping forever.
Nameless attributes such as "<a ='c'>" or unbalanced quotes "<a b='''''''c'>" can trigger this condition.
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Analysis
by VulDB Data Team • 07/16/2026
This vulnerability resides in the XML::Bare Perl module version 0.53 and earlier, where a critical parsing flaw leads to indefinite looping during XML attribute processing. The issue stems from the parserc_parse function which fails to properly advance its internal state cursor when encountering malformed attribute structures, creating an infinite loop condition that consumes system resources indefinitely. The vulnerability specifically manifests when processing nameless attributes or attributes with unbalanced quotation marks such as empty string attributes or improperly closed quoted values.
The technical root cause involves improper state management within the XML parsing logic where the parser maintains an internal cursor to track attribute parsing progress. When malformed attributes containing empty strings or unbalanced quotes are encountered, this cursor fails to advance through the parsing states, causing the function to repeatedly process the same malformed input without making forward progress. This represents a classic denial of service vulnerability that can be exploited by malicious actors to consume system resources and potentially cause application crashes or system instability.
From an operational standpoint, this vulnerability presents significant security implications for any Perl applications relying on XML::Bare for XML processing, particularly web applications that accept user input through XML data streams. Attackers can craft specifically malformed XML payloads containing empty attributes or unbalanced quotes to trigger the infinite loop condition, resulting in resource exhaustion and application unavailability. The vulnerability aligns with CWE-835 which specifically addresses infinite loops in software implementations and represents a failure in proper input validation and state management.
The impact extends beyond simple resource consumption as this vulnerability can be leveraged for denial of service attacks against web services, application servers, or any system processing XML data through the affected Perl module. Applications using XML::Bare for processing external XML inputs become vulnerable to exploitation, potentially affecting critical business systems where XML parsing is a core functionality. The attack surface includes web applications, API endpoints, and any system components that accept and process XML formatted data without proper input sanitization.
Security mitigations should focus on immediate patching of the XML::Bare module to version 0.54 or later where the parsing logic has been corrected to properly advance state cursors even when encountering malformed attributes. Organizations should implement input validation measures including XML schema validation and attribute normalization before processing external XML data. Network-level protections such as rate limiting and input filtering can provide additional defense in depth. The remediation process should also include comprehensive testing of XML processing components to ensure proper handling of edge cases and malformed inputs, following security best practices outlined in the OWASP XML Security guidelines and ATT&CK technique T1496 for resource exhaustion attacks.
The vulnerability demonstrates the critical importance of robust input validation and proper state management in parsing libraries, particularly those handling structured data formats like XML. It highlights the need for comprehensive testing of edge cases and malformed inputs during software development lifecycle phases to prevent such denial of service conditions from reaching production environments. Organizations should maintain updated security monitoring to detect potential exploitation attempts and ensure their systems can handle malformed input gracefully without entering infinite processing loops.