Bug 2545818 (CVE-2019-25777)

Summary: CVE-2019-25777 perl-yaml: perl-yaml: Arbitrary code execution via unrestricted package variable assignment
Product: [Other] Security Response Reporter: OSIDB Bzimport <bzimport>
Component: vulnerabilityAssignee: Product Security <prodsec-ir-bot>
Status: NEW --- QA Contact:
Severity: high Docs Contact:
Priority: high    
Version: unspecifiedCC: rhel-process-autobot, watson-tool-maintainers
Target Milestone: ---Keywords: Security
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Hardware: All   
OS: Linux   
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A flaw was found in perl-yaml. This vulnerability can lead to arbitrary code execution because the parser fails to restrict package variable modifications specified in YAML documents. An attacker capable of submitting crafted YAML input can overwrite internal configuration settings to enable code loading, allowing them to execute arbitrary Perl code within the running process.
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Description OSIDB Bzimport 2026-10-05 07:08:34 UTC 
YAML versions before 1.27_001 for Perl allow a loaded perl/glob document to replace any package variable, which can lead to arbitrary code execution.

A perl/glob document names a package and a symbol, and supplies the value assigned to it. Nothing restricts the name, so the target can be @INC or YAML's own load options.

A perl/glob document that sets $YAML::LoadCode or $YAML::UseCode turns on code loading, which is off by default, for every later Load() in the process. A perl/code document is then passed to a string eval, so an attacker who supplies two documents to separate Load() calls in one process can execute arbitrary Perl code.