GHSA-MC85-72GR-VM9F

Vulnerability from github – Published: 2026-07-10 00:03 – Updated: 2026-07-10 00:03
VLAI
Summary
Tesla has decompression bomb on response body
Details

Summary

Any Tesla client pipeline that includes Tesla.Middleware.DecompressResponse or Tesla.Middleware.Compression eagerly decompresses HTTP response bodies with no size limit. A server under attacker control (or reached via a redirect) can return a tiny gzip-encoded payload that expands into gigabytes of BEAM heap, crashing or freezing the calling process. Stacking multiple content-encoding tokens multiplies the amplification exponentially.

Details

decompress_body/2 in lib/tesla/middleware/compression.ex passes the full response body to :zlib.gunzip/1 or :zlib.unzip/1 with no cap on output size. The list of codec tokens comes from splitting the content-encoding header on commas, and decompress_body/2 recurses once per token. A response advertising content-encoding: gzip, gzip, gzip, gzip triggers four recursive decompression passes. Each gzip layer can expand its input roughly 1000x, so a 284-byte wire payload with four layers inflates to approximately 1 GB at the innermost pass, all materialised as a single binary in the caller's heap.

PoC

  1. Serve an HTTP response with content-encoding: gzip, gzip, gzip, gzip where the body is a 1 GB block of zeros compressed through four successive gzip passes.
  2. Send that response to a Tesla client whose pipeline includes Tesla.Middleware.DecompressResponse.
  3. decompress_body/2 recurses four times without any size check, materialising ~1 GB in the calling process's heap.
  4. Repeated or sufficiently large requests exhaust available memory and crash or freeze the node.

Impact

High severity (CVSS v4.0: 8.2). Any application using tesla 0.6.0 through 1.18.2 with Tesla.Middleware.DecompressResponse or Tesla.Middleware.Compression in its pipeline is vulnerable. The attacker only needs to control a server the client contacts, including via redirects. Fixed in tesla 1.18.3.

Configurations

The application must include Tesla.Middleware.DecompressResponse or Tesla.Middleware.Compression in its Tesla middleware pipeline.

Resources

  • Introduction commit: https://github.com/elixir-tesla/tesla/commit/5bd90bb5cf0d15e375edc2a66fa322292940fce2
  • Patch commit: https://github.com/elixir-tesla/tesla/commit/340f75b5d191dc747ef7ac6365bd002d1cd55a9d
Severity
8.2 (High)
CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N
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{
  "affected": [
    {
      "package": {
        "ecosystem": "Hex",
        "name": "tesla"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "0.6.0"
            },
            {
              "fixed": "1.18.3"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ]
    }
  ],
  "aliases": [
    "CVE-2026-48594"
  ],
  "database_specific": {
    "cwe_ids": [
      "CWE-409"
    ],
    "github_reviewed": true,
    "github_reviewed_at": "2026-07-10T00:03:23Z",
    "nvd_published_at": "2026-06-02T20:16:38Z",
    "severity": "HIGH"
  },
  "details": "### Summary\n\nAny Tesla client pipeline that includes `Tesla.Middleware.DecompressResponse` or `Tesla.Middleware.Compression` eagerly decompresses HTTP response bodies with no size limit. A server under attacker control (or reached via a redirect) can return a tiny gzip-encoded payload that expands into gigabytes of BEAM heap, crashing or freezing the calling process. Stacking multiple `content-encoding` tokens multiplies the amplification exponentially.\n\n### Details\n\n`decompress_body/2` in `lib/tesla/middleware/compression.ex` passes the full response body to `:zlib.gunzip/1` or `:zlib.unzip/1` with no cap on output size. The list of codec tokens comes from splitting the `content-encoding` header on commas, and `decompress_body/2` recurses once per token. A response advertising `content-encoding: gzip, gzip, gzip, gzip` triggers four recursive decompression passes. Each gzip layer can expand its input roughly 1000x, so a 284-byte wire payload with four layers inflates to approximately 1 GB at the innermost pass, all materialised as a single binary in the caller\u0027s heap.\n\n### PoC\n\n1. Serve an HTTP response with `content-encoding: gzip, gzip, gzip, gzip` where the body is a 1 GB block of zeros compressed through four successive gzip passes.\n2. Send that response to a Tesla client whose pipeline includes `Tesla.Middleware.DecompressResponse`.\n3. `decompress_body/2` recurses four times without any size check, materialising ~1 GB in the calling process\u0027s heap.\n4. Repeated or sufficiently large requests exhaust available memory and crash or freeze the node.\n\n### Impact\n\nHigh severity (CVSS v4.0: 8.2). Any application using `tesla` 0.6.0 through 1.18.2 with `Tesla.Middleware.DecompressResponse` or `Tesla.Middleware.Compression` in its pipeline is vulnerable. The attacker only needs to control a server the client contacts, including via redirects. Fixed in tesla 1.18.3.\n\n### Configurations\n\nThe application must include `Tesla.Middleware.DecompressResponse` or `Tesla.Middleware.Compression` in its Tesla middleware pipeline.\n\n### Resources\n\n* Introduction commit: https://github.com/elixir-tesla/tesla/commit/5bd90bb5cf0d15e375edc2a66fa322292940fce2\n* Patch commit: https://github.com/elixir-tesla/tesla/commit/340f75b5d191dc747ef7ac6365bd002d1cd55a9d",
  "id": "GHSA-mc85-72gr-vm9f",
  "modified": "2026-07-10T00:03:23Z",
  "published": "2026-07-10T00:03:23Z",
  "references": [
    {
      "type": "WEB",
      "url": "https://github.com/elixir-tesla/tesla/security/advisories/GHSA-mc85-72gr-vm9f"
    },
    {
      "type": "ADVISORY",
      "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-48594"
    },
    {
      "type": "WEB",
      "url": "https://github.com/elixir-tesla/tesla/commit/340f75b5d191dc747ef7ac6365bd002d1cd55a9d"
    },
    {
      "type": "WEB",
      "url": "https://cna.erlef.org/cves/CVE-2026-48594.html"
    },
    {
      "type": "PACKAGE",
      "url": "https://github.com/elixir-tesla/tesla"
    },
    {
      "type": "WEB",
      "url": "https://osv.dev/vulnerability/EEF-CVE-2026-48594"
    }
  ],
  "schema_version": "1.4.0",
  "severity": [
    {
      "score": "CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N",
      "type": "CVSS_V4"
    }
  ],
  "summary": "Tesla has decompression bomb on response body"
}



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