# CVE-2026-76875: PyPy pyexpat ExternalEntityParserCreate Use-After-Free

> Attackers can trigger memory corruption and potential code execution in PyPy applications by supplying crafted XML documents that exploit a use-after-free in the pyexpat module.

- **Severity:** Medium 6.3 (`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`)
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** Yes
- **Published:** 29 Sep 2026
- **Updated:** 2 Oct 2026
- **Also known as:** DEBIAN-CVE-2026-76875, GHSA-4h3r-h8c5-46cf, UBUNTU-CVE-2026-76875

## What is CVE-2026-76875?

CVE-2026-76875 is a medium-severity use after free vulnerability in PyPy, published on 29 Sep 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.

### Official description

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.

Weakness: CWE-416 (Use After Free)

## Which versions are affected by CVE-2026-76875?


## How do I fix CVE-2026-76875?

Upgrade to a fixed version.

## Is CVE-2026-76875 being exploited?

There is no known exploitation of CVE-2026-76875 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-76875 and fix it if it is affected.

What it is: CVE-2026-76875 is a medium-severity use after free vulnerability in PyPy, published on 29 Sep 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.
Exploitation: There is no known exploitation of CVE-2026-76875 in the wild and no public exploit code.

Affected product: PyPy. No package-level version data is available, so check the vendor advisory linked from the reference page.

Task:
1. Search the dependency manifests and lockfiles (for example package.json, package-lock.json, requirements.txt, poetry.lock, uv.lock, pom.xml, build.gradle, go.mod, Cargo.lock, Gemfile.lock) and any Dockerfiles for the affected packages, including transitive dependencies.
2. If an affected version is in use, upgrade it to the fixed version for its release line with the project's package manager, so the lockfile is regenerated. Prefer the smallest upgrade that fixes it.
3. If there is no fix, or the upgrade would break the build, do not guess: explain the risk and the safest workaround instead.
4. Run the tests and summarise what changed and why.
5. If nothing in the project is affected, say so and change nothing.

Reference: https://insights.sbomify.com/CVE-2026-76875/ (Markdown: https://insights.sbomify.com/CVE-2026-76875/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-76875
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-76875
- OSV: https://osv.dev/vulnerability/CVE-2026-76875

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-76875/
Summaries are generated and may contain mistakes; the official description above is the record.