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Detect invalid box size in avifRWStreamFinishBox() #3207

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Merged
wantehchang merged 1 commit into from
May 19, 2026
+10 −1
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Detect invalid box size in avifRWStreamFinishBox() #3207

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11 changes: 10 additions & 1 deletion src/stream.c
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Original file line number Diff line number Diff line change
Expand Up @@ -429,7 +429,16 @@ avifResult avifRWStreamWriteBox(avifRWStream * stream, const char * type, size_t
void avifRWStreamFinishBox(avifRWStream * stream, avifBoxMarker marker)
{
assert(stream->numUsedBitsInPartialByte == 0); // Byte alignment is required.
uint32_t noSize = avifHTONL((uint32_t)(stream->offset - marker));
size_t boxSize = stream->offset - marker;
// Since marker comes from a previous avifRWStreamWriteBox() or
// avifRWStreamWriteFullBox() call, boxSize must be >= the size of the size
// and type fields. This implies that boxSize cannot be equal to the two
// special values 0 and 1.
assert(boxSize >= sizeof(uint32_t) + 4);
if (boxSize > UINT32_MAX) {
abort();
}
uint32_t noSize = avifHTONL((uint32_t)boxSize);
memcpy(stream->raw->data + marker, &noSize, sizeof(uint32_t));
}

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