Bug 2555758 (CVE-2026-110680)

Summary: CVE-2026-110680 perl-Cpanel-JSON-XS: Out-of-bounds write during canonical encoding
Product: [Other] Security Response Reporter: OSIDB Bzimport <bzimport>
Component: vulnerabilityAssignee: Product Security DevOps Team <prodsec-dev>
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Priority: high    
Version: unspecifiedKeywords: Security
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OS: Linux   
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A flaw was found in perl-Cpanel-JSON-XS. When the canonical configuration is enabled, the keys of a tied or threads::shared hash are counted in a first pass before a second pass collects them for sorting. The encoder allocates a fixed 64-entry stack array or, for larger counts, a heap array sized based on the initial count. If the hash grows between these two passes and the second pass exceeds the allocated capacity, entries are written out of bounds before the counts are compared. This out-of-bounds write corrupts stack or heap memory. An attacker exploiting this race condition can crash the process, resulting in a Denial of Service (DoS) or potentially execute arbitrary code.
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Bug Depends On: 2556469, 2556470    
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Description OSIDB Bzimport 2026-10-19 18:34:40 UTC 
Cpanel::JSON::XS versions from 4.20 before 4.80 for Perl write out of bounds when a tied or shared hash grows during canonical encoding in encode_hv.

With canonical, the keys of a tied or threads::shared hash are counted before a second pass collects them for sorting. The encoder uses a fixed 64-entry stack array or, for larger counts, a heap array sized from the first pass. If the second pass exceeds that capacity, entries are written out of bounds before the counts are compared.

This corrupts stack or heap memory and can crash the process.