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Fix CVE-2026-3713: heap buffer overflow in pnm2png due to integer overflow in row_bytes #2

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Fix CVE-2026-3713: heap buffer overflow in pnm2png due to integer overflow in row_bytes #2

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11 changes: 9 additions & 2 deletions pngminus/pnm2png.c
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Original file line number Diff line number Diff line change
Expand Up @@ -357,12 +357,19 @@ BOOL do_pnm2png (png_struct *png_ptr, png_info *info_ptr,
if (packed_bitmap)
{
/* row data is as many bytes as can fit width x channels x bit_depth */
row_bytes = (width * channels * bit_depth + 7) / 8;
png_uint_32 pixels = (png_uint_32) (channels * bit_depth);
if (pixels == 0 || width > (0xFFFFFFFFU - 7) / pixels)
return FALSE; /* overflow */
row_bytes = (width * pixels + 7) / 8;
}
else
{
/* row_bytes is the width x number of channels x (bit-depth / 8) */
row_bytes = width * channels * ((bit_depth <= 8) ? 1 : 2);
png_uint_32 bytes_per_sample = (bit_depth <= 8) ? 1 : 2;
png_uint_32 pixel_bytes = (png_uint_32) channels * bytes_per_sample;
if (pixel_bytes == 0 || width > 0xFFFFFFFFU / pixel_bytes)
return FALSE; /* overflow */
row_bytes = width * pixel_bytes;
}

if ((row_bytes == 0) ||
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