Bug 2496031 (CVE-2025-15646)

Summary: CVE-2025-15646 HTML-Gumbo: HTML::Gumbo: Information disclosure through HTML template processing
Product: [Other] Security Response Reporter: OSIDB Bzimport <bzimport>
Component: vulnerabilityAssignee: Product Security <prodsec-ir-bot>
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Version: unspecifiedKeywords: Security
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OS: Linux   
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A flaw was found in HTML::Gumbo, a Perl module used for parsing HTML. This vulnerability allows for information disclosure due to a type confusion error when processing HTML input containing a `<template>` element. An attacker could exploit this by providing specially crafted HTML, leading to the disclosure of sensitive data from the application's memory.
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Bug Depends On: 2496536    
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Description OSIDB Bzimport 2026-07-01 16:03:26 UTC 
HTML::Gumbo versions before 0.19 for Perl disclose heap memory via type confusion.

Support for the <template> element was added to libgumbo 0.10.0 in 2015, but the walk_tree function in lib/HTML/Gumbo.xs was not updated to support it. The element was treated as a text-node, where strlen() over-reads the heap block that the pointer addresses.

Any caller that runs parse() with the default format => 'string', or with format => 'tree', on input containing a <template> element serializes the over-read bytes into the returned result, disclosing bounded heap contents. format => 'callback' reaches a croak on the unhandled node type and is unaffected.