CVE-2026-114501: Pillow: Arrow export leaks stale heap memory when PILLOW_ALIGNMENT > 1
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 PILLOWALIGNMENT makes alignedlinesize 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.
Affected Software
Remediation
Recommended actions to resolve this vulnerability, in priority order.
- Upgrade
Upgrade
Pillowto a version that resolves this vulnerability.Fixed in 13.0.0
Event History
Frequently Asked Questions
Which deployments are exposed to this disclosure?
Applications using Pillow versions from 11.2.1 up to, but not including, 13.0.0 are affected when they configure PILLOW_ALIGNMENT greater than 1 and export images to Arrow. The impact is disclosure of image data from another user or other stale process memory.
What must happen for an attacker to obtain leaked data?
The application must export an image to Arrow while aligned row sizes or offsets cause the image storage not to be tightly contiguous. The exported buffer may then contain uninitialized row padding, bytes before the first image row, or stale heap contents from previously freed images.
Is the default configuration affected?
The described condition requires PILLOW_ALIGNMENT to be greater than 1. The provided information does not indicate that deployments using the default alignment setting are affected.
What is the remediation?
Upgrade Pillow to version 13.0.0, which fixes the issue. If an immediate upgrade is not possible, avoid configuring PILLOW_ALIGNMENT greater than 1 or avoid exporting affected images to Arrow.