Bug 2543127 (CVE-2026-76875)

Summary: CVE-2026-76875 pypy: pypy: Memory corruption via use-after-free in pyexpat
Product: [Other] Security Response Reporter: OSIDB Bzimport <bzimport>
Component: vulnerabilityAssignee: Product Security DevOps Team <prodsec-dev>
Status: NEW --- QA Contact:
Severity: medium Docs Contact:
Priority: medium    
Version: unspecifiedKeywords: Security
Target Milestone: ---   
Target Release: ---   
Hardware: All   
OS: Linux   
Whiteboard:
Fixed In Version: Doc Type: ---
Doc Text:
A flaw was found in PyPy's pyexpat module. A remote attacker can cause memory corruption by supplying a specially crafted Extensible Markup Language (XML) document to an application that processes external entity sub-parsers without keeping a reference to the parent parser. This situation triggers a use-after-free condition, where the parent parser's memory is released prematurely while still referenced by the sub-parser, resulting in invalid memory access during parsing.
 Story Points: ---
Clone Of: Environment:
Last Closed: Type: ---
Regression: --- Mount Type: ---
Documentation: --- CRM:
Verified Versions: Category: ---
oVirt Team: --- RHEL 7.3 requirements from Atomic Host:
Cloudforms Team: --- Target Upstream Version:
Embargoed:
Bug Depends On: 2544462, 2544463, 2544464    
Bug Blocks:    

Description OSIDB Bzimport 2026-09-29 12:58:32 UTC 
PyPy before versions 3.11.16 and 3.12.14 contains a use-after-free vulnerability in the pyexpat module's ExternalEntityParserCreate function that allows attackers to corrupt memory by supplying a crafted XML document to applications that create external-entity sub-parsers without retaining a reference to the parent parser. The child parser retains a raw C back-pointer to the parent parser struct while PyPy's tracing garbage collector can free the parent's C struct, causing bundled libexpat to dereference the freed pointer on every parsed token, producing memory corruption.