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BIT-pillow-2026-54060 — Pillow: `FontFile.compile()`: `Image.new()` called without `_decompression_bomb_check()`

2026-10-01T15:31:06.028548+00:00

Affected: Bitnami: pillow

Pillow is a Python imaging library. Prior to 12.3.0, PIL/FontFile.py FontFile.compile() assembled per-glyph images into a combined bitmap with Image.new("1", (xsize, ysize)) without calling Image._decompression_bomb_check(), allowing a font to trigger excessive allocation during conversion or saving. This issue is fixed in version 12.3.0.

CVE-2026-54060 — Pillow: `FontFile.compile()`: `Image.new()` called without `_decompression_bomb_check()`

2026-10-01T15:31:06.028659+00:00

Affected: python-pillow Pillow

GHSA-5x94-69rx-g8h2 — Pillow: `FontFile.compile()`: `Image.new()` called without `_decompression_bomb_check()`

2026-10-01T15:31:06.028719+00:00

Affected: PyPI: pillow

## Description

`PIL/FontFile.py` `FontFile.compile()` assembles per-glyph images into a single combined bitmap using `Image.new("1", (xsize, ysize))` without calling `Image._decompression_bomb_check()`. This is the base-class method shared by both `BdfFontFile` and `PcfFontFile`, and it is triggered whenever a loaded font is converted to an `ImageFont` or saved.

Neither `BdfFontFile.BdfFontFile(fp)` nor `PcfFontFile.PcfFontFile(fp)` is registered with `Image.register_open()`, so Pillow's standard decompression bomb guard never fires for font objects. The compile step is the final opportunity to check the combined allocation — and it has no check.

**Vulnerable code (`PIL/FontFile.py` lines ~64–92):**

```python def compile(self) -> None: if self.bitmap: return

h = w = maxwidth = 0 lines = 1 for glyph in self.glyph: # up to 256 glyph slots if glyph: d, dst, src, im = glyph h = max(h, src[3] - src[1]) # max glyph height — attacker-controlled w = w + (src[2] - src[0]) if w > WIDTH: # WIDTH = 800 lines += 1 w = src[2] - src[0] maxwidth = max(maxwidth, w)

xsize = maxwidth # ≤ 800 (capped by WIDTH constant) ysize = lines * h # ← lines(256) × h(65535) = 16,776,960

if xsize == 0 and ysize == 0: return

self.ysize = h # NO _decompression_bomb_check() here…

PYSEC-2026-2254

2026-10-01T15:31:06.028842+00:00

Affected: PyPI: pillow