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Critical, CVSS 9.8amended

Pillow multi-frame loaders can reuse stale native image storage after mode transitions

CVE-2026-96639GHSA-v9pv-5gc8-w2m6

What to do

Vendor fix available. Upgrade each affected package to the fixed version on its release line (pillow 13.0.0; pillow 13.0.0), redeploy, then verify what is actually installed.

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

  • Bitnami pillow

    Affected
    >= 11.0.0, < 13.0.0
    Fixed in
    13.0.0

  • PyPI pillow

    Affected
    >= 11.0.0, < 13.0.0
    Fixed in
    13.0.0

Sources

Severity and exploitation
Exploitation
No confirmed exploitation recorded. Patch Next marks exploitation only from CISA KEV.
CVSS
9.8 · CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
EPSS
  • CVE-2026-96639: 0.66% estimated exploitation activity in the next 30 days; percentile 51.58 (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.

Summary Pillow multi-frame image loaders can retain native `ImagingCore` storage allocated for one frame while changing the Python-side image `mode` and decoder tiles for a later frame. If frame 0 allocates storage for a narrow mode such as `L`, and a later frame of the same dimensions switches to a wider mode such as `RGB` or `CMYK`, Pillow may decode wider pixels into the stale narrow native buffer. This causes native out-of-bounds writes and process crashes. In the MPO/JPEG path, I also demonstrated command execution in matching Python/Pillow runtime profiles through Pillow's documented `ImageSequence.Iterator` + `frame.load()` path.

Details The root cause appears to be that `ImageFile.load_prepare()` only reallocates native storage when `_im is None`. It does not verify that the retained native `ImagingCore` storage still matches `self.mode` and `self.size`. Several multi-frame `seek()` / `_open()` paths can update `self._mode` and decoder tiles for a later frame without…

Dates and revisions
Published by the source
Last modified by the source
Source last checked
  1. Revision 8 · amended ·

    Amended from osv record BIT-pillow-2026-96639

  2. Revision 7 · amended ·

    Amended from osv record PYSEC-2026-4339

  3. Revision 6 · amended ·

    Amended from osv record GHSA-v9pv-5gc8-w2m6

  4. Revision 5 · amended ·

    Amended from osv record PYSEC-2026-4339

  5. Revision 4 · amended ·

    Amended from osv record GHSA-v9pv-5gc8-w2m6

  6. Revision 3 · amended ·

    Amended from ghsa record GHSA-v9pv-5gc8-w2m6

  7. Revision 2 · amended ·

    Amended from osv record GHSA-v9pv-5gc8-w2m6

  8. Revision 1 · created ·

    Published from ghsa record GHSA-v9pv-5gc8-w2m6

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-2026-96639

Advisory: Pillow multi-frame loaders can reuse stale native image storage after mode transitions
IDs: CVE-2026-96639, GHSA-v9pv-5gc8-w2m6
Record: https://patchnext.com/advisories/cve-2026-96639 (revision 8, source checked 30 Oct 2026, 07:20 UTC)
Inventory: none attached. This brief comes from a public page and does not say whether any deployment is affected.
Severity: Critical (CVSS 9.8)
Exploitation: no confirmed exploitation recorded. Patch Next confirms exploitation only from CISA KEV.
Vendor response: Vendor fix available; fixed versions by package: pillow 13.0.0; pillow 13.0.0. A vendor fix does not mean a deployment is fixed.

## Affected components
- Bitnami pillow: affected >= 11.0.0, < 13.0.0; fixed in 13.0.0
- PyPI pillow: affected >= 11.0.0, < 13.0.0; fixed in 13.0.0

## Suggested inspection (read-only)
- Bitnami pillow: check the installed version with your package manager.
- `python -m pip show pillow`: prints the installed version. Run with the environment that serves production active.

## Supported action
Upgrade each affected component to a fixed version on its release line. For a transitive dependency, upgrade the parent package or add an override or constraint, then regenerate the lockfile. Redeploy every environment that ran an affected version.

## Required regression checks
- Run the test suite and a production build.
- Exercise the features that depend on pillow.
- 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://github.com/advisories/GHSA-v9pv-5gc8-w2m6 (GitHub-reviewed advisory GHSA-v9pv-5gc8-w2m6 lists affected ranges: PyPI pillow >=11.0.0 <13.0.0)
- Verified: https://osv.dev/vulnerability/GHSA-v9pv-5gc8-w2m6 (OSV record GHSA-v9pv-5gc8-w2m6 lists affected ranges: PyPI pillow >=11.0.0 <13.0.0 (fixed))
- Verified: https://osv.dev/vulnerability/PYSEC-2026-4339 (OSV record PYSEC-2026-4339 lists affected ranges: PyPI pillow >=11.0.0 <13.0.0 (fixed))
- Verified: https://osv.dev/vulnerability/BIT-pillow-2026-96639 (OSV record BIT-pillow-2026-96639 lists affected ranges: Bitnami pillow >=11.0.0 <13.0.0 (fixed))

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