webp/decode: validate VP8L dimensions before decoding (upstream security fix)#21
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Merge golang/image@7a0cfdab: verify VP8L chunk dimensions before decoding when seenVP8X is true, to prevent DoS via malicious images with a small VP8X header but a huge VP8L chunk. Uses bufio.Peek to read the VP8L header for validation without consuming the reader.
Copilot created this pull request from a session on behalf of
kovidgoyal
July 14, 2026 00:37
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Merges golang/image@7a0cfdab into
webp/decode.go.A malicious image could pair a small VP8X header (declaring tiny dimensions) with a huge VP8L chunk. The old code decoded the entire VP8L chunk before checking dimensions, enabling a DoS via memory exhaustion.
Changes
bufio.Reader.Peekand runvp8l.DecodeConfigon them to extract dimensions — before callingvp8l.Decodebufio.NewReaderwrapping is equivalent to what thevp8lpackage does internally anyway; the reader is passed through tovp8l.DecodeunchangederrInvalidFormatimmediately without decoding the payload