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Do not read any further than necessary when decoding BMP images with RLE8 compression #9824

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Merged
hugovk merged 1 commit into from
Jul 28, 2026
+5 −4
Merged

Do not read any further than necessary when decoding BMP images with RLE8 compression #9824

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9 changes: 5 additions & 4 deletions src/PIL/BmpImagePlugin.py
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Original file line number Diff line number Diff line change
Expand Up @@ -371,19 +371,20 @@ def decode(self, buffer: Image.DecoderInput) -> tuple[int, int]:
x = len(data) % self.state.xsize
else:
# absolute mode
data_count = min(dest_length - len(data), byte[0])
if rle4:
# 2 pixels per byte, padded up to a whole byte
byte_count = (byte[0] + 1) // 2
byte_count = (data_count + 1) // 2
bytes_read = self.fd.read(byte_count)
for i, byte_read in enumerate(bytes_read):
data += o8(byte_read >> 4)
if 2 * i + 1 < byte[0]:
if i * 2 + 1 < data_count:
data += o8(byte_read & 0x0F)
else:
byte_count = byte[0]
byte_count = data_count
bytes_read = self.fd.read(byte_count)
data += bytes_read
if len(bytes_read) < byte_count:
if len(bytes_read) < byte_count or len(data) == dest_length:
break
x += byte[0]

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