Brotli certificate decompression can allocate up to 1 GiB before authentication

The built-in Brotli certificate decompressor (enabled by the non-default `brotli` crate feature) bounded the size of the decompressed output, but accepted a peer-selected history window. Brotli's large-window extension was enabled, so a five-byte header could cause an allocation of 1 GiB. A peer can abort a process whose allocator cannot satisfy that request. No trusted certificate is required by the attacker. Affected configurations are: - clients that enable the `brotli` feature and connect to a malicious server, and - servers that enable the `brotli` feature and request client certificates. Applications that do not enable the `brotli` feature are not affected.

Source published

14 Oct 2026 12:00:00 UTC

Source modified

14 Oct 2026 13:30:02 UTC

Observed here

24 Oct 2026 13:19:54 UTC

Source terms

OSV · upstream source license applies

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CVSS_V3 · CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:L