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Medium, CVSS 6.9amended

Heap-based Buffer Overflow in MicroPython

CVE-2024-8946GHSA-74qm-4v7r-jw2f

What to do

Vendor response not established. Follow the primary source's mitigation guidance and check back for a fix.

This page has no inventory attached, so it cannot say whether you are affected. A vendor fix is not proof that your deployment is fixed.

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Affected packages

  • PyPI micropython-string

    Affected
    <= 0.1
    Fixed in
    no fixed version recorded

  • PyPI micropython-os-path

    Affected
    <= 0.1.3
    Fixed in
    no fixed version recorded

  • PyPI micropython-copy

    Affected
    <= 3.3.3.post3
    Fixed in
    no fixed version recorded

  • PyPI micropython-io

    Affected
    <= 0.1
    Fixed in
    no fixed version recorded

Sources

Severity and exploitation
Exploitation
No confirmed exploitation recorded. Patch Next marks exploitation only from CISA KEV.
CVSS 4.0
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/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X · score source
EPSS
  • CVE-2024-8946: 1.01% estimated exploitation activity in the next 30 days; percentile 63.31 (FIRST EPSS, 2026-11-03). This is a model estimate, not proof of exploitation or customer exposure.
Source description

As published by the source; long descriptions are shortened.

A vulnerability was found in MicroPython 1.23.0. It has been classified as critical. Affected is the function mpvfsumount of the file extmod/vfs.c of the component VFS Unmount Handler. The manipulation leads to heap-based buffer overflow. It is possible to launch the attack remotely. The exploit has been disclosed to the public and may be used. The name of the patch is 29943546343c92334e8518695a11fc0e2ceea68b. It is recommended to apply a patch to fix this issue. In the VFS unmount process, the comparison between the mounted path string and the unmount requested string is based solely on the length of the unmount string, which can lead to a heap buffer overflow read.

Dates and revisions
Published by the source
Last modified by the source
Source last checked
  1. Revision 3 · amended ·

    Amended from ghsa record GHSA-74qm-4v7r-jw2f

  2. Revision 2 · amended ·

    Reviewed OSV alias/range/CVSS4 correction; package source scopes and original publication preserved. No customer finding resolved.

  3. Revision 1 · created ·

    Published from osv record GHSA-74qm-4v7r-jw2f

Agent brief

Preview the exact text before you copy it. Commands are read-only suggestions; review them before running anything.

# Patch Next advisory brief: CVE-2024-8946

Advisory: Heap-based Buffer Overflow in MicroPython
IDs: CVE-2024-8946, GHSA-74qm-4v7r-jw2f
Record: https://patchnext.com/advisories/cve-2024-8946 (revision 3, source checked 26 Oct 2026, 13:18 UTC)
Inventory: none attached. This brief comes from a public page and does not say whether any deployment is affected.
Severity: Medium (CVSS 6.9)
Exploitation: no confirmed exploitation recorded. Patch Next confirms exploitation only from CISA KEV.
Vendor response: Vendor response not established. A vendor fix does not mean a deployment is fixed.

## Affected components
- PyPI micropython-string: affected <= 0.1
- PyPI micropython-os-path: affected <= 0.1.3
- PyPI micropython-copy: affected <= 3.3.3.post3
- PyPI micropython-io: affected <= 0.1

## Suggested inspection (read-only)
- `python -m pip show micropython-string`: prints the installed version. Run with the environment that serves production active.
- `python -m pip show micropython-os-path`: prints the installed version. Run with the environment that serves production active.
- `python -m pip show micropython-copy`: prints the installed version. Run with the environment that serves production active.
- `python -m pip show micropython-io`: prints the installed version. Run with the environment that serves production active.

## Supported action
No complete vendor fix is recorded. Follow the primary source's mitigation guidance and check this record again before closing anything.

## Required regression checks
- Run the test suite and a production build.
- Exercise the features that depend on micropython-string, micropython-os-path, micropython-copy, micropython-io.
- Repeat the inspection and confirm that only fixed versions remain installed.

## Rollback considerations
- Keep the previous lockfile and deployment artifact. Rolling back reinstates the vulnerable version, so apply any documented mitigation while you fix forward.

## Unresolved questions
- Which deployments run an affected version?
- Exploitation status can change. Check again before lowering the priority.
- Mark the work resolved only after the fixed version is verified in production.

## Sources
- Verified: https://osv.dev/vulnerability/GHSA-74qm-4v7r-jw2f (OSV record GHSA-74qm-4v7r-jw2f lists affected ranges: PyPI micropython-copy >=0 =0 =0 =0 <=0.1)
- Verified: https://github.com/advisories/GHSA-74qm-4v7r-jw2f (GitHub-reviewed advisory GHSA-74qm-4v7r-jw2f lists affected ranges: PyPI micropython-copy >=0 =0 =0 =0 <=0.1)

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