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Findings

RUSTSEC-2026-0348

Brotli certificate decompression can allocate up to 1 GiB before authentication

Published Oct 14, 2026 · updated Oct 14, 2026

The built-in Brotli certificate decompressor (enabled by the non-default 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 feature and connect to a malicious server, and - servers that enable the feature and request client certificates. Applications that do not enable the feature are not affected.

Timeline

Detection, updates, and resolution for this record.

  1. Oct 14, 2026 · GitHub Advisory Database

    Detected

    The built-in Brotli certificate decompressor (enabled by the non-default 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 attac

  2. Oct 14, 2026 · GitHub Advisory Database

    Fix available

    rustls fixed in 0.23.46

  3. Oct 14, 2026 · GitHub Advisory Database

    Fix available

    rustls fixed in 0.23.46

  4. Oct 14, 2026 · GitHub Advisory Database

    Updated

    The built-in Brotli certificate decompressor (enabled by the non-default 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 attac

Affected

  • crates.io rustls0.23.9 → 0.23.46

Sources

References