Live › vulnerability › GHSA-h2v8-394m-p7vv
Go to dashboardWhen the optional Brotli feature is enabled, a peer can send a compressed certificate whose header requests a 1 GiB decompression window, forcing a large allocation before any authentication. An attacker can make the process abort or run out of memory, a denial of service.
Summary written from the sources below. Check the originals before acting.
First seen by InfraStack 2026-10-27 16:10 UTC. All times on this page are UTC.
Only applications that enable the feature of rustls are exposed, because that is the only path that decodes Brotli-compressed certificates. Client applications face malicious servers, and server applications that request client certificates face malicious clients. Applications that keep the default feature set can skip this issue.
brotli| Product | Ecosystem | Affected | Fixed in |
|---|---|---|---|
| rustls | cargo | < 0.23.46 | 0.23.46 |
| rustls | cargo | >= 0.24.0-dev.1, < 0.24.0-dev.2 | 0.24.0-dev.2 |
brotli feature of rustls is enabled in Cargo.toml or in the lockfile feature set (cargo tree -e features -i rustls).Cargo.lock with cargo tree -i rustls, comparing against 0.23.46 and 0.24.0-dev.2.0.23.46 or later on the 0.23 line, or to 0.24.0-dev.2 or later on the 0.24 development line.brotli feature disabled, since it is off by default.Each row is the first time that source carried this signal. The analyst’s rows are its own findings.
The built-in (but disabled by default) Brotli certificate decoder bounds the output buffer but accepts an input-selected history window. A header of five bytes can specify a 1 GiB window allocation. A peer can abort a process whose allocator cannot satisfy that request. A client must enable Brotli and connect to the peer; a server must enable Brotli and request a client certificate. Neither direction requires a trusted attacker certificate.
rustls calls BrotliDecompress which enables Brotli's large-window extension. rustls applies a limit to certificates, but this applies to the decompressed result, and not to any internal allocations the process requires.
Client applications that enable the brotli feature will be vulnerable to malicious servers. Server applications that enable the brotli feature and enable client authentication will be vulnerable to malicious clients.
Potential for denial of service due to memory exhaustion from peers sending malicious Brotli-encoded certificates, for applications that enable Brotli decompression.
Thanks to OpenAI [email protected] for the disclosure.
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