CVE-2026-76875
PyPy pyexpat ExternalEntityParserCreate Use-After-Free
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.
Fixes and workarounds
Fix
The reporting source identifies this reference as a patch. Check the advisory for affected versions and supported release branches.
Source: CNA: VulnCheckFix
The reporting source identifies this reference as a patch. Check the advisory for affected versions and supported release branches.
Source: CNA: VulnCheckAffected products and versions
| Product | Versions | Authority |
|---|---|---|
| PyPy PyPy pypy/pypy
github |
≥ 0; < 3.11.16 (affected, semver) ≥ 3.12.0; < 3.12.14 (affected, semver) Other versions: unaffected |
CNA: VulnCheck |
Version ranges are source assertions. Check the vendor advisory and your installed configuration before determining exposure.
CVSS assessments
| Version / score | Vector | Authority |
|---|---|---|
| 4.0 / 6.3 medium |
CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:N/VI:L/VA:N/SC:N/SI:N/SA:N | CNA: VulnCheck |
| 3.1 / 5.3 medium |
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:N | CNA: VulnCheck |
Exploit evidence
No exploit evidence in collected sources. This is not proof of no exploitation.
References
- https://doc.pypy.org/release-v8.0.0.htmlCNA: VulnCheck · release-notes
- https://github.com/pypy/pypy/releases/tag/release-pypy3.12-v8.0.0CNA: VulnCheck · patch, release-notes
- https://github.com/pypy/pypy/releases/tag/release-pypy3.11-v8.0.0CNA: VulnCheck · patch, release-notes
- https://www.vulncheck.com/advisories/pypy-pyexpat-externalentityparsercreate-use-after-freeCNA: VulnCheck · third-party-advisory
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