XML::Bare Perl Parser Infinite Loop in Malformed Attributes

Executive Summary

CVE-2026-13401 is an infinite loop vulnerability in the XML::Bare Perl module's C parser. It occurs when parsing malformed XML attributes, such as nameless attributes or unbalanced quotes. The parser gets stuck in a loop because it fails to advance its position after encountering certain malformed inputs, causing it to consume CPU indefinitely.

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Detection Guidance

To detect this vulnerability, monitor for processes consuming excessive CPU time, particularly those running XML::Bare or Perl scripts parsing XML input. Check for malformed XML inputs triggering infinite loops, such as attributes with nameless values or unbalanced quotes like <a ='c'> or <a b='''''''c'>.

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Impact Analysis

This vulnerability can cause a denial of service by consuming excessive CPU resources. If exploited, it may lead to system slowdowns or crashes. Since the parser holds the Perl interpreter, it cannot be interrupted by Perl-level signals like alarms, making it difficult to mitigate once triggered.

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Compliance Impact

This vulnerability could indirectly impact compliance with standards like GDPR or HIPAA by enabling denial-of-service (DoS) attacks. An infinite loop in XML parsing may cause system unavailability, potentially violating availability requirements in these regulations. However, the CVE itself does not directly reference compliance standards.

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Mitigation Strategies

Immediately update XML::Bare to a patched version (0.53 or later) that fixes the infinite loop in parserc_parse. If updating is not possible, restrict XML input processing to trusted sources only and implement timeouts for XML parsing operations.

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