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BREW-aider-CVE-2026-112893 — Pillow: Invalid free in FreeType glyph rendering when a stroker is active

Affected: Homebrew: aider

### Summary When text is drawn with a non-zero stroke width, Pillow creates a FreeType stroker and then loads each glyph. If `FT_Load_Glyph` fails for a glyph, the cleanup path calls `FT_Done_Glyph` on the `glyph` variable. That variable is not initialized before the first measurement loop, and in the render loop it is not reset to NULL after each glyph is freed. A malformed font loaded from untrusted bytes can force the load error and reach this free. This is a latent memory-safety defect; whether it crashes depends on the value in the uninitialized or stale pointer.

### Details `glyph` is declared without a NULL initializer:

- `src/_imagingft.c:848`

The first measurement loop can jump to `glyph_error` before `glyph` is ever assigned:

- `src/_imagingft.c:1010-1013`

In the render loop the glyph is freed at the end of each iteration and not set back to NULL:

- `src/_imagingft.c:1242`

The cleanup frees it whenever a stroker exists:

- `src/_imagingft.c:1253-1256`

`ImageFont.truetype` accepts a file object or bytes, so the font is attacker-suppliable.

### PoC This needs `fontTools` and any base TTF (the example uses one bundled with Pillow's tests). It rewrites glyph "A" to claim 5000 contours in a glyph body far too short for them, so `FT_Load_Glyph` returns an error while the face still opens.

```python import struct from fontTools.ttLib import TTFont from PIL import Image, ImageFont, ImageDraw

SRC = "Tests/fonts/FreeMono.ttf" # any TTF works as a base tt…

fkie_cve-2026-112893

Pillow is a Python imaging library. From 10.0.0 until 13.0.0, Pillow can free an invalid glyph pointer during FreeType rendering with an active stroker. If FT_Load_Glyph fails, cleanup may call FT_Done_Glyph on an uninitialized or stale glyph variable. An attacker can supply a malformed font as untrusted bytes to an application that draws text with a nonzero stroke width, forcing the glyph-load failure path. This can corrupt memory or crash the process. This issue is fixed in version 13.0.0.

GHSA-j4m9-6w36-pw47 — Pillow: Invalid free in FreeType glyph rendering when a stroker is active

Affected: PyPI: pillow