---
id: RUSTSEC-2026-0348
aliases:
  - GHSA-h2v8-394m-p7vv
title: >-
  Brotli certificate decompression can allocate up to 1 GiB before
  authentication
summary: >-
  Brotli certificate decompression can allocate up to 1 GiB before
  authentication
severity: low
cvss: 3.7
cvssVector: 'CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:L'
vendor: rustls
product: rustls
ecosystem: rust
affected:
  - 'rustls >= 0.23.9, < 0.23.46'
patched:
  - rustls 0.23.46
published: '2026-10-14'
updated: '2026-10-14'
sourceUpdated: '2026-10-14T13:30:02.480925286Z'
source: OSV
sourceUrl: 'https://osv.dev/vulnerability/RUSTSEC-2026-0348'
references:
  - url: 'https://crates.io/crates/rustls'
  - url: 'https://rustsec.org/advisories/RUSTSEC-2026-0348.html'
  - url: 'https://github.com/rustls/rustls/pull/3297'
tags:
  - osv
  - rust
ingestedAt: '2026-10-15T11:47:08.230Z'
---

## Overview

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.

## Affected packages

- `rustls >= 0.23.9, < 0.23.46`

## Remediation

Upgrade to a patched release:

- `rustls 0.23.46`