GHSA-mvh2-crg5-v77c

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GHSA-mvh2-crg5-v77c

Summary: Netty SPDY zlib header block continues decoded expansion after maxHeaderSize truncation

Details: ### Summary Netty SPDY header decoding continues inflating zlib-compressed header blocks after the raw header parser has already exceeded maxHeaderSize and marked the frame truncated. At commit b2d2137c4404af425bf9d5d601a62576f5c06925, a 12,253-byte compressed SPDY header block can declare and inflate a 12 MiB header-name field with maxHeaderSize=16, forcing compression-amplified decode and skip work in a reachable SpdyFrameCodec pipeline. ### PoC [poc.zip](https://github.com/user-attachments/files/28445780/poc.zip) run with: ```bash bash ./poc/run.sh ``` expected output: ```text NETTY_SPDY_ZLIB_DECODED_AFTER_LIMIT_TRIGGERED compressed_bytes=12253 declared_name_length=12582912 max_header_size=16 truncated=true invalid=false ``` The fingerprint means the compressed input was fully consumed while the raw header parser ended with `truncated=true` and `invalid=false` after processing the oversized decoded name. That specific state distinguishes this bug from a generic setup failure: the maxHeaderSize guard fired, but the zlib/raw decode path still inflated and skipped the full 12 MiB declared name. ### Impact A remote unauthenticated peer that can speak SPDY to a Netty pipeline containing SpdyFrameCodec can send a small compressed HEADERS block that expands into much larger raw header data after the configured maxHeaderSize limit has already been exceeded. The attack requires a reachable SPDY codec, ordinary transport setup such as TCP and optional TLS, and no independent compressed-frame-size or connection-rate limit ahead of SpdyFrameCodec. The satisfied protocol guards are straightforward: the HEADERS frame uses a nonzero stream id and length >= 4, the decoder factory selects the zlib decoder, the payload uses the SPDY dictionary, and the raw block appends a zero-length value so the already-truncated frame reaches END_HEADER_BLOCK. The user-visible effect is denial of service through compression-amplified CPU and allocation churn.

References: https://github.com/netty/netty/security/advisories/GHSA-mvh2-crg5-v77c, https://nvd.nist.gov/vuln/detail/CVE-2026-55833, https://github.com/netty/netty/commit/5b68c61f37aa4a3045cba624cbea239655c9003b, https://github.com/netty/netty/commit/bb2ff68a1fb71cb4b0eb9a9e17b66c52aff680c6, https://github.com/netty/netty, https://github.com/netty/netty/releases/tag/netty-4.1.136.Final, https://github.com/netty/netty/releases/tag/netty-4.2.16.Final