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Medium, CVSS 5.9amended

Pillow: Heap use-after-free when encoding TIFF to an in-memory buffer

CVE-2026-112396GHSA-4rr5-89j8-mwwm

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
    >= 11.3.0, < 13.0.0
    Fixed in
    13.0.0

  • PyPI pillow

    Affected
    >= 11.3.0, < 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
5.9 · CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:H
EPSS
  • CVE-2026-112396: 0.69% estimated exploitation activity in the next 30 days; percentile 53.00 (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 Saving an image as TIFF to an in-memory buffer can trigger a heap use-after-free if libtiff rejects a tag at encode time. When `TIFFWriteScanline` fails, the encoder frees its output buffer but leaves the libtiff handle open. Later, when the encoder object is torn down, `TIFFClose` flushes buffered bytes through the write callback and writes into the freed buffer. An application that re-encodes attacker-influenced images to TIFF in memory can be crashed and is a candidate for remote code execution.

Details The failure path in `ImagingLibTiffEncode` frees `clientstate->data` for the in-memory case but does not close the TIFF or null `clientstate->tiff` (the file-descriptor branch just above it does set `tiff = NULL`): - `src/libImaging/TiffDecode.c:1041-1046` Teardown then calls `ImagingLibTiffEncodeCleanup`, which runs `TIFFClose(tiff)` because `tiff` is still set: - `src/encode.c:99-101` - `src/libImaging/TiffDecode.c:955` `TIFFClose` flushes through…

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-2026-112396

  2. Revision 7 · amended ·

    Amended from osv record PYSEC-2026-4328

  3. Revision 6 · amended ·

    Amended from osv record GHSA-4rr5-89j8-mwwm

  4. Revision 5 · amended ·

    Amended from ghsa record GHSA-4rr5-89j8-mwwm

  5. Revision 4 · amended ·

    Amended from osv record BIT-pillow-2026-112396

  6. Revision 3 · amended ·

    Amended from osv record GHSA-4rr5-89j8-mwwm

  7. Revision 2 · amended ·

    Amended from osv record GHSA-4rr5-89j8-mwwm

  8. Revision 1 · created ·

    Published from ghsa record GHSA-4rr5-89j8-mwwm

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-2026-112396

Advisory: Pillow: Heap use-after-free when encoding TIFF to an in-memory buffer
IDs: CVE-2026-112396, GHSA-4rr5-89j8-mwwm
Record: https://patchnext.com/advisories/cve-2026-112396 (revision 8, source checked 28 Oct 2026, 06:45 UTC)
Inventory: none attached. This brief comes from a public page and does not say whether any deployment is affected.
Severity: Medium (CVSS 5.9)
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 >= 11.3.0, < 13.0.0; fixed in 13.0.0
- PyPI pillow: affected >= 11.3.0, < 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-4rr5-89j8-mwwm (GitHub-reviewed advisory GHSA-4rr5-89j8-mwwm lists affected ranges: PyPI pillow >=11.3.0 <13.0.0)
- Verified: https://osv.dev/vulnerability/GHSA-4rr5-89j8-mwwm (OSV record GHSA-4rr5-89j8-mwwm lists affected ranges: PyPI pillow >=11.3.0 <13.0.0 (fixed))
- Verified: https://osv.dev/vulnerability/BIT-pillow-2026-112396 (OSV record BIT-pillow-2026-112396 lists affected ranges: Bitnami pillow >=11.3.0 <13.0.0 (fixed))
- Verified: https://osv.dev/vulnerability/PYSEC-2026-4328 (OSV record PYSEC-2026-4328 lists affected ranges: PyPI pillow >=11.3.0 <13.0.0 (fixed))

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