8.9

CVSS Score

4.0

-

CVSS Score

Basic Information

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CVE-2026-25990

CVE-2026-25990: Pillow has an out-of-bounds write when loading PSD images

Pillow is a Python imaging library. From 10.3.0 to before 12.1.1, n out-of-bounds write may be triggered when loading a specially crafted PSD image. This vulnerability is fixed in 12.1.1.

(GitHub Advisory)

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CVE-2026-25990

CVE-2026-25990:

8.9

CVSS Score

4.0

-

CVSS Score

Basic Information

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Technical Details

Package Name	Ecosystem	Vulnerable Versions	First Patched Version
pillow	pip	>= 10.3.0, < 12.1.1	12.1.1

Technical Details

Vulnerability Intelligence
Miggo AI

Root Cause Analysis

The vulnerability is an out-of-bounds write caused by a lack of validation on tile offsets when processing image files in the Pillow library. The core of the vulnerability lies in the C-level function _setimage within src/decode.c, which is responsible for handling image tiles during the decoding process. The patch 54ba4db542ad3c7b918812a4e2d69c27735a3199 clearly shows the addition of checks to ensure the tile offsets (xoff and yoff) are not negative. Without these checks, a malicious image file could specify negative offsets, causing the function to write data before the start of the allocated memory buffer.

The Python-level entry point for this vulnerability is the load() method of the PsdImageFile class. When a user opens a crafted PSD image and the load() method is called (either explicitly or implicitly), it triggers the vulnerable C decoding function, resulting in the out-of-bounds write. The analysis of the patch also revealed a similar vulnerability in the encoding path in src/encode.c, which was fixed in the same commit. Therefore, both the decoding and encoding _setimage functions are identified as vulnerable, with the PsdImageFile.load method being the primary way to trigger the vulnerability during runtime.

Vulnerable functions

_setimage

src/decode.c

This C function is responsible for setting the image tile during the decoding process. The vulnerability lies in the lack of validation for negative offsets (`state->xoff` and `state->yoff`). A crafted image could provide negative values for these offsets, causing the decoder to write pixel data outside the boundaries of the destination image buffer, leading to an out-of-bounds write.

PsdImageFile.load

src/PIL/PsdImagePlugin.py

This Python method is the entry point for loading the pixel data of a PSD image. When called on a specially crafted PSD file, it invokes the vulnerable `_setimage` C function, leading to the out-of-bounds write. This function would appear in a Python profiler's stack trace during the exploitation of this vulnerability.

_setimage

src/encode.c

Similar to its counterpart in `decode.c`, this C function for encoding images also lacked checks for negative tile offsets. While the primary reported vulnerability is in decoding, this function was also patched to prevent a potential out-of-bounds write during image saving operations if provided with malicious tile parameters.

Vulnerability Intelligence
Miggo AI

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WAF Protection Rules

WAF Rule

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Reasoning

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