Rustls: Brotli certificate decompression can allocate an attacker-controlled amount of memory up to 1 GiB before authentication.

{
  "id": "7c1630999e34b43540bd7d4559e2a36f31a802b5e9a0243623f1a02bb46d5b11",
  "url": "https://osv.dev/vulnerability/GHSA-h2v8-394m-p7vv",
  "method": "structured",
  "payload": {
    "kind": "advisory",
    "title": "Rustls: Brotli certificate decompression can allocate an attacker-controlled amount of memory up to 1 GiB before authentication.",
    "summary": "### Summary 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. ### Details 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. ### Impact 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. ### Acknowledgement Thanks to OpenAI [OutboundDisclosures@openai.com](mailto:OutboundDisclosures@openai.com) for the disclosure.",
    "evidence": "osv:GHSA-h2v8-394m-p7vv",
    "products": [
      {
        "name": {
          "value": "rustls",
          "evidence": "/affected/0/package/name"
        },
        "prerequisites": [],
        "fixed_versions": [
          {
            "value": "0.23.46",
            "evidence": "/affected/0/ranges"
          }
        ],
        "affected_versions": []
      },
      {
        "name": {
          "value": "rustls",
          "evidence": "/affected/1/package/name"
        },
        "prerequisites": [],
        "fixed_versions": [
          {
            "value": "0.24.0-dev.2",
            "evidence": "/affected/1/ranges"
          }
        ],
        "affected_versions": []
      }
    ],
    "severity": "low",
    "structured": {
      "id": "GHSA-h2v8-394m-p7vv",
      "aliases": [
        "GHSA-h2v8-394m-p7vv",
        "RUSTSEC-2026-0348"
      ],
      "metrics": [
        {
          "type": "CVSS_V3",
          "score": "CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:L"
        }
      ],
      "affected": [
        {
          "ranges": [
            {
              "type": "SEMVER",
              "events": [
                {
                  "introduced": "0"
                },
                {
                  "fixed": "0.23.46"
                }
              ]
            }
          ],
          "package": {
            "name": "rustls",
            "purl": "pkg:cargo/rustls",
            "ecosystem": "crates.io"
          },
          "database_specific": {
            "source": "https://github.com/github/advisory-database/blob/main/advisories/github-reviewed/2026/10/GHSA-h2v8-394m-p7vv/GHSA-h2v8-394m-p7vv.json"
          }
        },
        {
          "ranges": [
            {
              "type": "SEMVER",
              "events": [
                {
                  "introduced": "0.24.0-dev.1"
                },
                {
                  "fixed": "0.24.0-dev.2"
                }
              ]
            }
          ],
          "package": {
            "name": "rustls",
            "purl": "pkg:cargo/rustls",
            "ecosystem": "crates.io"
          },
          "database_specific": {
            "source": "https://github.com/github/advisory-database/blob/main/advisories/github-reviewed/2026/10/GHSA-h2v8-394m-p7vv/GHSA-h2v8-394m-p7vv.json"
          }
        }
      ],
      "modified": "2026-10-27T16:15:05.337819489Z",
      "provider": "osv",
      "references": [
        "https://github.com/rustls/rustls/security/advisories/GHSA-h2v8-394m-p7vv",
        "https://github.com/rustls/rustls/pull/3297",
        "https://github.com/rustls/rustls/pull/3354",
        "https://github.com/rustls/rustls/commit/1aa987af37d0d79b98781d345895ac0059ce345c",
        "https://github.com/rustls/rustls/commit/402b7b78b7ae87d59e19cf07ee07f3fc19e6537e",
        "https://github.com/rustls/rustls",
        "https://github.com/rustls/rustls/releases/tag/v/0.23.46",
        "https://rustsec.org/advisories/RUSTSEC-2026-0348.html"
      ],
      "provider_metadata": {
        "cwe_ids": [
          "CWE-770"
        ],
        "severity": "LOW",
        "github_reviewed": true,
        "nvd_published_at": null,
        "github_reviewed_at": "2026-10-27T16:08:36Z"
      }
    },
    "related_cves": [],
    "security_relevant": true,
    "severity_evidence": "/database_specific/severity"
  },
  "source_id": "core-osv",
  "document_id": 462860,
  "published_at": "2026-10-27T16:08:36+00:00"
}