spdystream EUVD-2026-23298

The SPDY/3 frame parser in spdystream does not validate attacker-controlled counts and lengths before allocating memory. A remote peer that can send SPDY frames to a service using spdystream can cause the process to allocate gigabytes of memory with a small number of malformed control frames, leading to an out-of-memory crash.

Three allocation paths in the receive side are affected:

1. SETTINGS entry count -- The SETTINGS frame reader reads a 32-bit

numSettings from the payload and allocates a slice of that size without checking it against the declared frame length. An attacker can set numSettings to a value far exceeding the actual payload, triggering a large allocation before any setting data is read.

1. Header count -- parseHeaderValueBlock reads a 32-bit

numHeaders from the decompressed header block and allocates an http.Header map of that size with no upper bound.

1. Header field size -- Individual header name and value lengths are

read as 32-bit integers and used directly as allocation sizes with no validation.

Because SPDY header blocks are zlib-compressed, a small on-the-wire payload can decompress into attacker-controlled bytes that the parser interprets as 32-bit counts and lengths. A single crafted frame is enough to exhaust process memory.

Impact

Any program that accepts SPDY connections using spdystream -- directly or through a dependent library -- is affected. A remote peer that can send SPDY frames to the service can crash the process with a single crafted SPDY control frame, causing denial of service.

Affected versions

github.com/moby/spdystream <= v0.5.0

Fix

v0.5.1 addresses the receive-side allocation bugs and adds related hardening:

Core fixes:

• SETTINGS entry-count validation -- The SETTINGS frame reader now

checks that numSettings is consistent with the declared frame length (numSettings <= (length-4)/8) before allocating.

• Header count limit -- parseHeaderValueBlock enforces a maximum

number of headers per frame (default: 1000).

• Header field size limit -- Individual header name and value

lengths are checked against a per-field size limit (default: 1 MiB) before allocation.

• Connection closure on protocol error -- The connection read loop

now closes the underlying net.Conn when it encounters an InvalidControlFrame error, preventing further exploitation on the same connection.

Additional hardening:

• Write-side bounds checks -- All frame write methods now verify

that payloads fit within the 24-bit length field, preventing the library from producing invalid frames.

Configurable limits:

• Callers can adjust the defaults using NewConnectionWithOptions or

the lower-level spdy.NewFramerWithOptions with functional options: WithMaxControlFramePayloadSize, WithMaxHeaderFieldSize, and WithMaxHeaderCount.