Bug 2555759 (CVE-2026-110674)

Summary: CVE-2026-110674 perl-Cpanel-JSON-XS: Type confusion via duplicate non-ASCII bare keys
Product: [Other] Security Response Reporter: OSIDB Bzimport <bzimport>
Component: vulnerabilityAssignee: Product Security DevOps Team <prodsec-dev>
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Priority: medium    
Version: unspecifiedKeywords: Security
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OS: Linux   
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A flaw was found in perl-Cpanel-JSON-XS. When the allow_barekey configuration (enabled by the relaxed setting) is active, a bare key containing a non-ASCII byte is stored as UTF-8 but looked up as raw bytes. This allows a repeated key to bypass the duplicate-key check and replace the earlier value. Under the dupkeys_as_arrayref configuration, a bare repeating key replaces the array that normally collects a key's values with a plain value. If a subsequent quoted repeat occurs, the parser attempts to push onto that value as if it were an array. If a JSON integer is present there, it is erroneously dereferenced as a pointer. An attacker can exploit this type confusion by submitting crafted JSON payloads to dereference an arbitrary address, resulting in a Denial of Service (DoS).
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Bug Depends On: 2556471, 2556472    
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Description OSIDB Bzimport 2026-10-19 18:34:59 UTC 
Cpanel::JSON::XS versions from 4.33 before 4.80 for Perl miss duplicate non-ASCII bare keys, allowing type confusion under dupkeys_as_arrayref in decode_hv.

With allow_barekey, which relaxed enables, a bare key containing a non-ASCII byte is stored as UTF-8 but looked up as raw bytes, so a repeated key escapes the duplicate-key check and replaces the earlier value.

From 4.41, under dupkeys_as_arrayref, a bare repeat replaces the array that collects a key's values with a plain value, and the next quoted repeat pushes onto that value as if it were an array. A JSON integer there is dereferenced as a pointer.

Untrusted JSON decoded with relaxed and dupkeys_as_arrayref can crash the process or dereference an address chosen by a JSON number.