# CVE-2024-8948: MicroPython objint.c mpz_as_bytes heap-based overflow

> A heap-based buffer overflow in MicroPython allows remote attackers to execute arbitrary code or cause denial of service via integer conversion.

- **Severity:** Medium 6.9 (`CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:L/VI:L/VA:L/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:** 17 Sep 2024
- **Updated:** 17 Sep 2024
- **Also known as:** DEBIAN-CVE-2024-8948, GHSA-vh3x-525m-jp4r, PYSEC-2024-87, PYSEC-2024-88, PYSEC-2024-89, UBUNTU-CVE-2024-8948

## What is CVE-2024-8948?

CVE-2024-8948 is a medium-severity memory corruption vulnerability in MicroPython, published on 17 Sep 2024. An attacker can exploit it over the internet without logging in, with no action from the victim.

### Official description

A vulnerability was found in MicroPython 1.23.0. It has been rated as critical. Affected by this issue is the function mpz_as_bytes of the file py/objint.c. The manipulation leads to heap-based buffer overflow. The attack may be launched remotely. The exploit has been disclosed to the public and may be used. The patch is identified as 908ab1ceca15ee6fd0ef82ca4cba770a3ec41894. It is recommended to apply a patch to fix this issue. In micropython objint component, converting zero from int to bytes leads to heap buffer-overflow-write at mpz_as_bytes.

Weakness: CWE-787 (Out-of-bounds Write), CWE-122 (Heap-based Buffer Overflow)

## Which versions are affected by CVE-2024-8948?

9 open source packages ship an affected version, including micropython-copy, micropython-io and micropython-os. It affects 1 product.


| Package | Ecosystem | Affected | Fixed in |
| --- | --- | --- | --- |
| `micropython-copy` | PyPI | All versions | None |
| `micropython-copy` | PyPI | All versions to 3.3.3.post3 | None |
| `micropython-copy` | PyPI | All versions to 3.3.3.post3 | None |
| `micropython-io` | PyPI | All versions | None |
| `micropython-io` | PyPI | All versions to 0.1 | None |
| `micropython-io` | PyPI | All versions to 0.1 | None |
| `micropython-os` | PyPI | All versions | None |
| `micropython-os` | PyPI | All versions to 0.8 | None |
| `micropython-os` | PyPI | All versions to 0.8 | None |

Products: Micropython Micropython.

## How do I fix CVE-2024-8948?

Apply the vendor's patch.

## Is CVE-2024-8948 being exploited?

It is not confirmed as exploited in the wild, but public exploit code for CVE-2024-8948 exists.

## Other vulnerabilities in MicroPython

- [CVE-2023-7158](https://insights.sbomify.com/CVE-2023-7158/): MicroPython objslice.c slice_indices heap-based overflow (high 7.3)
- [CVE-2024-8946](https://insights.sbomify.com/CVE-2024-8946/): MicroPython VFS Unmount vfs.c mp_vfs_umount heap-based overflow (medium 6.9)
- [CVE-2024-8947](https://insights.sbomify.com/CVE-2024-8947/): MicroPython objarray.c use after free (medium 6.3)
- [CVE-2023-7152](https://insights.sbomify.com/CVE-2023-7152/): MicroPython modselect.c poll_set_add_fd use after free (medium 5.5)
- [CVE-2026-1998](https://insights.sbomify.com/CVE-2026-1998/): micropython runtime.c mp_import_all memory corruption (medium 4.8)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2024-8948 and fix it if it is affected.

What it is: CVE-2024-8948 is a medium-severity memory corruption vulnerability in MicroPython, published on 17 Sep 2024. An attacker can exploit it over the internet without logging in, with no action from the victim.
Exploitation: It is not confirmed as exploited in the wild, but public exploit code for CVE-2024-8948 exists.

Affected packages and fixed versions:
- micropython-copy (PyPI): affected all versions; no fix listed
- micropython-copy (PyPI): affected all versions up to 3.3.3.post3; no fix listed
- micropython-copy (PyPI): affected all versions up to 3.3.3.post3; no fix listed
- micropython-io (PyPI): affected all versions; no fix listed
- micropython-io (PyPI): affected all versions up to 0.1; no fix listed
- micropython-io (PyPI): affected all versions up to 0.1; no fix listed
- micropython-os (PyPI): affected all versions; no fix listed
- micropython-os (PyPI): affected all versions up to 0.8; no fix listed
- micropython-os (PyPI): affected all versions up to 0.8; no fix listed

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-2024-8948/ (Markdown: https://insights.sbomify.com/CVE-2024-8948/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2024-8948
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2024-8948
- OSV: https://osv.dev/vulnerability/CVE-2024-8948

---
From sbomify Insights: https://insights.sbomify.com/CVE-2024-8948/
Summaries are generated and may contain mistakes; the official description above is the record.