PyPy pyexpat ExternalEntityParserCreate Use-After-Free
Key facts
- Attack vector
- Network
- Privileges required
- None
- User interaction
- None
- Attack complexity
- Low
- Attack requirements
- Present
- Impact type
- —
- Confidentiality · integrity · availability
- None · Low · None
- Fix status
- Fixed
Attack profile from CVSS 4.0 · CNA. Fix status from CNA.
Summary
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.
Why it matters now
SSVC decision points
CISA ADP · SSVC 2.0.3
- Exploitation
- None
- Automatable
- Yes
- Technical impact
- Partial
The decision (Track, Attend, Act) also depends on your mission and well-being impact; see CISA's SSVC guide.
Affected products
Remediation
- Fix · CNA PyPy (PyPy) Fixed in 3.11.16, 3.12.14
Vendor assessments
Timeline
- 2026-10-02 Threatist record created from CVE-2026-76875
- 2026-10-03 Alias added: GHSA-4h3r-h8c5-46cf
References
More PyPy vulnerabilities
- TI-2022-17508 The Keccak XKCP SHA-3 reference implementation before fdc6fef has an integer overflow and… CVSS 3.1CRITICAL 9.8
Sources
- CVE-2026-76875 · CVE Program
- CVE-2026-76875 · NVD
- FIRST EPSS
- GHSA-4h3r-h8c5-46cf · GitHub Advisory Database · CC BY 4.0
- CVE-2026-76875 · Red Hat security data · CC BY 4.0
This product uses the NVD API but is not endorsed or certified by the NVD. Sources and licences